diff --git a/src/Bundle.js b/src/Bundle.js
index 0fd7656..aac7790 100644
--- a/src/Bundle.js
+++ b/src/Bundle.js
@@ -290,13 +290,13 @@ export default class Bundle {
 		//
 		// This doesn't apply if the bundle is exported as ES6!
 		let allBundleExports = blank();
-		let isVarDeclaration = blank();
+		let isReassignedVarDeclaration = blank();
 		let varExports = blank();
 		let getterExports = [];
 
 		this.orderedModules.forEach( module => {
-			module.varDeclarations.forEach( name => {
-				isVarDeclaration[ module.replacements[ name ] || name ] = true;
+			module.reassignments.forEach( name => {
+				isReassignedVarDeclaration[ module.replacements[ name ] || name ] = true;
 			});
 		});
 
@@ -306,7 +306,7 @@ export default class Bundle {
 				.forEach( name => {
 					const canonicalName = this.traceExport( this.entryModule, name );
 
-					if ( isVarDeclaration[ canonicalName ] ) {
+					if ( isReassignedVarDeclaration[ canonicalName ] ) {
 						varExports[ name ] = true;
 
 						// if the same binding is exported multiple ways, we need to
diff --git a/src/Module.js b/src/Module.js
index 9964ae2..461c20b 100644
--- a/src/Module.js
+++ b/src/Module.js
@@ -64,7 +64,7 @@ export default class Module {
 
 		this.replacements = blank();
 
-		this.varDeclarations = [];
+		this.reassignments = [];
 
 		this.definitions = blank();
 		this.definitionPromises = blank();
@@ -202,20 +202,35 @@ export default class Module {
 				this.definitions[ name ] = statement;
 			});
 
-			statement.scope.varDeclarations.forEach( name => {
-				this.varDeclarations.push( name );
-			});
-
 			keys( statement.modifies ).forEach( name => {
 				( this.modifications[ name ] || ( this.modifications[ name ] = [] ) ).push( statement );
 			});
 		});
 
+		// discover variables that are reassigned inside function
+		// bodies, so we can keep bindings live, e.g.
+		//
+		//   export var count = 0;
+		//   export function incr () { count += 1 }
+		let reassigned = blank();
+		this.statements.forEach( statement => {
+			keys( statement.reassigns ).forEach( name => {
+				reassigned[ name ] = true;
+			});
+		});
+
 		// if names are referenced that are neither defined nor imported
 		// in this module, we assume that they're globals
 		this.statements.forEach( statement => {
 			if ( statement.isReexportDeclaration ) return;
 
+			// while we're here, mark reassignments
+			statement.scope.varDeclarations.forEach( name => {
+				if ( reassigned[ name ] && !~this.reassignments.indexOf( name ) ) {
+					this.reassignments.push( name );
+				}
+			});
+
 			keys( statement.dependsOn ).forEach( name => {
 				if ( !this.definitions[ name ] && !this.imports[ name ] ) {
 					this.bundle.assumedGlobals[ name ] = true;
diff --git a/src/Statement.js b/src/Statement.js
index d4117e1..ad66b15 100644
--- a/src/Statement.js
+++ b/src/Statement.js
@@ -8,6 +8,14 @@ function isIife ( node, parent ) {
 	return parent && parent.type === 'CallExpression' && node === parent.callee;
 }
 
+function isFunctionDeclaration ( node, parent ) {
+	// `function foo () {}`
+	if ( node.type === 'FunctionDeclaration' ) return true;
+
+	// `var foo = function () {}` - same thing for present purposes
+	if ( node.type === 'FunctionExpression' && parent.type === 'VariableDeclarator' ) return true;
+}
+
 export default class Statement {
 	constructor ( node, module, start, end ) {
 		this.node = node;
@@ -22,6 +30,8 @@ export default class Statement {
 		this.dependsOn = blank();
 		this.stronglyDependsOn = blank();
 
+		this.reassigns = blank();
+
 		this.isIncluded = false;
 
 		this.isImportDeclaration = node.type === 'ImportDeclaration';
@@ -117,22 +127,34 @@ export default class Statement {
 		//    calledImmediately();
 		//
 		// ...but it's better than nothing
-		let depth = 0;
+		let readDepth = 0;
+
+		// This allows us to track whether a modifying statement (i.e. assignment
+		// /update expressions) need to be captured
+		let writeDepth = 0;
 
 		if ( !this.isImportDeclaration ) {
 			walk( this.node, {
 				enter: ( node, parent ) => {
 					if ( node._scope ) {
-						if ( !scope.isBlockScope && !isIife( node, parent ) ) depth += 1;
+						if ( !scope.isBlockScope ) {
+							if ( !isIife( node, parent ) ) readDepth += 1;
+							if ( isFunctionDeclaration( node, parent ) ) writeDepth += 1;
+						}
+
 						scope = node._scope;
 					}
 
-					this.checkForReads( scope, node, parent, !depth );
-					this.checkForWrites( scope, node );
+					this.checkForReads( scope, node, parent, !readDepth );
+					this.checkForWrites( scope, node, writeDepth );
 				},
 				leave: ( node, parent ) => {
 					if ( node._scope ) {
-						if ( !scope.isBlockScope && !isIife( node, parent ) ) depth -= 1;
+						if ( !scope.isBlockScope ) {
+							if ( !isIife( node, parent ) ) readDepth -= 1;
+							if ( isFunctionDeclaration( node, parent ) ) writeDepth -= 1;
+						}
+
 						scope = scope.parent;
 					}
 				}
@@ -171,7 +193,7 @@ export default class Statement {
 		}
 	}
 
-	checkForWrites ( scope, node ) {
+	checkForWrites ( scope, node, writeDepth ) {
 		const addNode = ( node, isAssignment ) => {
 			let depth = 0; // determine whether we're illegally modifying a binding or namespace
 
@@ -207,9 +229,26 @@ export default class Statement {
 						this.module.exports.default.isModified = true;
 					}
 				}
+
+				// we track updates/reassignments to variables, to know whether we
+				// need to rewrite it later from `foo` to `exports.foo` to keep
+				// bindings live
+				if (
+					depth === 0 &&
+					writeDepth > 0 &&
+					!scope.contains( node.name )
+				) {
+					this.reassigns[ node.name ] = true;
+				}
 			}
 
-			if ( node.type === 'Identifier' ) {
+			// we only care about writes that happen a) at the top level,
+			// or b) inside a function that could be immediately invoked.
+			// Writes inside named functions are only relevant if the
+			// function is called, in which case we don't need to do
+			// anything (but we still need to call checkForWrites to
+			// catch illegal reassignments to imported bindings)
+			if ( writeDepth === 0 && node.type === 'Identifier' ) {
 				this.modifies[ node.name ] = true;
 			}
 		};
diff --git a/test/form/exclude-unnecessary-modifications/_config.js b/test/form/exclude-unnecessary-modifications/_config.js
new file mode 100644
index 0000000..2b3de2b
--- /dev/null
+++ b/test/form/exclude-unnecessary-modifications/_config.js
@@ -0,0 +1,3 @@
+module.exports = {
+	description: 'statements that modify definitions within unused functions are excluded'
+};
diff --git a/test/form/exclude-unnecessary-modifications/_expected/amd.js b/test/form/exclude-unnecessary-modifications/_expected/amd.js
new file mode 100644
index 0000000..84befa4
--- /dev/null
+++ b/test/form/exclude-unnecessary-modifications/_expected/amd.js
@@ -0,0 +1,28 @@
+define(function () { 'use strict';
+
+	var foo = {};
+
+	mutate1( foo );
+
+	// should be included
+	[ 'a', 'b', 'c' ].forEach( function ( letter, i ) {
+		foo[ letter ] = i;
+	});
+
+	[ 'd', 'e', 'f' ].forEach( ( letter, i ) => {
+		foo[ letter ] = i;
+	});
+
+	function mutate1 () {
+		foo.mutated = 1;
+	}
+
+	({
+		mutate2: function () {
+			foo.mutated = 2;
+		}
+	}).mutate2();
+
+	console.log( foo );
+
+});
diff --git a/test/form/exclude-unnecessary-modifications/_expected/cjs.js b/test/form/exclude-unnecessary-modifications/_expected/cjs.js
new file mode 100644
index 0000000..596c910
--- /dev/null
+++ b/test/form/exclude-unnecessary-modifications/_expected/cjs.js
@@ -0,0 +1,26 @@
+'use strict';
+
+var foo = {};
+
+mutate1( foo );
+
+// should be included
+[ 'a', 'b', 'c' ].forEach( function ( letter, i ) {
+	foo[ letter ] = i;
+});
+
+[ 'd', 'e', 'f' ].forEach( ( letter, i ) => {
+	foo[ letter ] = i;
+});
+
+function mutate1 () {
+	foo.mutated = 1;
+}
+
+({
+	mutate2: function () {
+		foo.mutated = 2;
+	}
+}).mutate2();
+
+console.log( foo );
diff --git a/test/form/exclude-unnecessary-modifications/_expected/es6.js b/test/form/exclude-unnecessary-modifications/_expected/es6.js
new file mode 100644
index 0000000..a88d21e
--- /dev/null
+++ b/test/form/exclude-unnecessary-modifications/_expected/es6.js
@@ -0,0 +1,24 @@
+var foo = {};
+
+mutate1( foo );
+
+// should be included
+[ 'a', 'b', 'c' ].forEach( function ( letter, i ) {
+	foo[ letter ] = i;
+});
+
+[ 'd', 'e', 'f' ].forEach( ( letter, i ) => {
+	foo[ letter ] = i;
+});
+
+function mutate1 () {
+	foo.mutated = 1;
+}
+
+({
+	mutate2: function () {
+		foo.mutated = 2;
+	}
+}).mutate2();
+
+console.log( foo );
diff --git a/test/form/exclude-unnecessary-modifications/_expected/iife.js b/test/form/exclude-unnecessary-modifications/_expected/iife.js
new file mode 100644
index 0000000..0fd4c40
--- /dev/null
+++ b/test/form/exclude-unnecessary-modifications/_expected/iife.js
@@ -0,0 +1,28 @@
+(function () { 'use strict';
+
+	var foo = {};
+
+	mutate1( foo );
+
+	// should be included
+	[ 'a', 'b', 'c' ].forEach( function ( letter, i ) {
+		foo[ letter ] = i;
+	});
+
+	[ 'd', 'e', 'f' ].forEach( ( letter, i ) => {
+		foo[ letter ] = i;
+	});
+
+	function mutate1 () {
+		foo.mutated = 1;
+	}
+
+	({
+		mutate2: function () {
+			foo.mutated = 2;
+		}
+	}).mutate2();
+
+	console.log( foo );
+
+})();
diff --git a/test/form/exclude-unnecessary-modifications/_expected/umd.js b/test/form/exclude-unnecessary-modifications/_expected/umd.js
new file mode 100644
index 0000000..1c2bb78
--- /dev/null
+++ b/test/form/exclude-unnecessary-modifications/_expected/umd.js
@@ -0,0 +1,32 @@
+(function (global, factory) {
+	typeof exports === 'object' && typeof module !== 'undefined' ? factory() :
+	typeof define === 'function' && define.amd ? define(factory) :
+	factory();
+}(this, function () { 'use strict';
+
+	var foo = {};
+
+	mutate1( foo );
+
+	// should be included
+	[ 'a', 'b', 'c' ].forEach( function ( letter, i ) {
+		foo[ letter ] = i;
+	});
+
+	[ 'd', 'e', 'f' ].forEach( ( letter, i ) => {
+		foo[ letter ] = i;
+	});
+
+	function mutate1 () {
+		foo.mutated = 1;
+	}
+
+	({
+		mutate2: function () {
+			foo.mutated = 2;
+		}
+	}).mutate2();
+
+	console.log( foo );
+
+}));
diff --git a/test/form/exclude-unnecessary-modifications/foo.js b/test/form/exclude-unnecessary-modifications/foo.js
new file mode 100644
index 0000000..2280631
--- /dev/null
+++ b/test/form/exclude-unnecessary-modifications/foo.js
@@ -0,0 +1,37 @@
+var foo = {};
+
+mutate1( foo );
+
+// should be included
+[ 'a', 'b', 'c' ].forEach( function ( letter, i ) {
+	foo[ letter ] = i;
+});
+
+[ 'd', 'e', 'f' ].forEach( ( letter, i ) => {
+	foo[ letter ] = i;
+});
+
+function mutate1 () {
+	foo.mutated = 1;
+}
+
+({
+	mutate2: function () {
+		foo.mutated = 2;
+	}
+}).mutate2();
+
+// should be excluded
+var mutate2 = function () {
+	foo.mutated = 2;
+}
+
+function unused1 () {
+	foo.wat = 'nope';
+}
+
+function unused2 () {
+	mutate1( foo );
+}
+
+export default foo;
diff --git a/test/form/exclude-unnecessary-modifications/main.js b/test/form/exclude-unnecessary-modifications/main.js
new file mode 100644
index 0000000..03d6edf
--- /dev/null
+++ b/test/form/exclude-unnecessary-modifications/main.js
@@ -0,0 +1,2 @@
+import foo from './foo';
+console.log( foo );
diff --git a/test/form/exported-empty-vars/_config.js b/test/form/exported-empty-vars/_config.js
deleted file mode 100644
index fa0287c..0000000
--- a/test/form/exported-empty-vars/_config.js
+++ /dev/null
@@ -1,6 +0,0 @@
-module.exports = {
-	description: 'removes empty var declarations that are exported',
-	options: {
-		moduleName: 'myBundle'
-	}
-};
diff --git a/test/form/exported-empty-vars/_expected/amd.js b/test/form/exported-empty-vars/_expected/amd.js
deleted file mode 100644
index c0f1472..0000000
--- a/test/form/exported-empty-vars/_expected/amd.js
+++ /dev/null
@@ -1,8 +0,0 @@
-define(['exports'], function (exports) { 'use strict';
-
-	exports.foo = 42;
-
-	exports.bar = 43;
-	exports.baz = 44;
-
-});
diff --git a/test/form/exported-empty-vars/_expected/cjs.js b/test/form/exported-empty-vars/_expected/cjs.js
deleted file mode 100644
index 4011bd7..0000000
--- a/test/form/exported-empty-vars/_expected/cjs.js
+++ /dev/null
@@ -1,6 +0,0 @@
-'use strict';
-
-exports.foo = 42;
-
-exports.bar = 43;
-exports.baz = 44;
diff --git a/test/form/exported-empty-vars/_expected/es6.js b/test/form/exported-empty-vars/_expected/es6.js
deleted file mode 100644
index 4b76753..0000000
--- a/test/form/exported-empty-vars/_expected/es6.js
+++ /dev/null
@@ -1,9 +0,0 @@
-var foo;
-foo = 42;
-
-var bar;
-var baz;
-bar = 43;
-baz = 44;
-
-export { foo, bar, baz };
diff --git a/test/form/exported-empty-vars/_expected/iife.js b/test/form/exported-empty-vars/_expected/iife.js
deleted file mode 100644
index 63c56b2..0000000
--- a/test/form/exported-empty-vars/_expected/iife.js
+++ /dev/null
@@ -1,8 +0,0 @@
-(function (exports) { 'use strict';
-
-	exports.foo = 42;
-
-	exports.bar = 43;
-	exports.baz = 44;
-
-})((this.myBundle = {}));
diff --git a/test/form/exported-empty-vars/bar.js b/test/form/exported-empty-vars/bar.js
deleted file mode 100644
index b8818da..0000000
--- a/test/form/exported-empty-vars/bar.js
+++ /dev/null
@@ -1,6 +0,0 @@
-var bar, baz;
-
-bar = 43;
-baz = 44;
-
-export { bar, baz };
diff --git a/test/form/exported-empty-vars/foo.js b/test/form/exported-empty-vars/foo.js
deleted file mode 100644
index 2c71d30..0000000
--- a/test/form/exported-empty-vars/foo.js
+++ /dev/null
@@ -1,2 +0,0 @@
-export var foo;
-foo = 42;
diff --git a/test/form/exported-empty-vars/main.js b/test/form/exported-empty-vars/main.js
deleted file mode 100644
index 21ee721..0000000
--- a/test/form/exported-empty-vars/main.js
+++ /dev/null
@@ -1,2 +0,0 @@
-export { foo } from './foo';
-export { bar, baz } from './bar';
diff --git a/test/form/exports-at-end-if-possible/_config.js b/test/form/exports-at-end-if-possible/_config.js
new file mode 100644
index 0000000..a898bc7
--- /dev/null
+++ b/test/form/exports-at-end-if-possible/_config.js
@@ -0,0 +1,7 @@
+module.exports = {
+	description: 'exports variables at end, if possible',
+	options: {
+		moduleName: 'myBundle'
+	},
+	// solo: true
+};
diff --git a/test/form/exports-at-end-if-possible/_expected/amd.js b/test/form/exports-at-end-if-possible/_expected/amd.js
new file mode 100644
index 0000000..2612901
--- /dev/null
+++ b/test/form/exports-at-end-if-possible/_expected/amd.js
@@ -0,0 +1,11 @@
+define(['exports'], function (exports) { 'use strict';
+
+	var FOO = 'foo';
+
+	console.log( FOO );
+	console.log( FOO );
+	console.log( FOO );
+
+	exports.FOO = FOO;
+
+});
diff --git a/test/form/exports-at-end-if-possible/_expected/cjs.js b/test/form/exports-at-end-if-possible/_expected/cjs.js
new file mode 100644
index 0000000..57d55d3
--- /dev/null
+++ b/test/form/exports-at-end-if-possible/_expected/cjs.js
@@ -0,0 +1,9 @@
+'use strict';
+
+var FOO = 'foo';
+
+console.log( FOO );
+console.log( FOO );
+console.log( FOO );
+
+exports.FOO = FOO;
diff --git a/test/form/exports-at-end-if-possible/_expected/es6.js b/test/form/exports-at-end-if-possible/_expected/es6.js
new file mode 100644
index 0000000..b42b4e4
--- /dev/null
+++ b/test/form/exports-at-end-if-possible/_expected/es6.js
@@ -0,0 +1,7 @@
+var FOO = 'foo';
+
+console.log( FOO );
+console.log( FOO );
+console.log( FOO );
+
+export { FOO };
diff --git a/test/form/exports-at-end-if-possible/_expected/iife.js b/test/form/exports-at-end-if-possible/_expected/iife.js
new file mode 100644
index 0000000..d1b29c8
--- /dev/null
+++ b/test/form/exports-at-end-if-possible/_expected/iife.js
@@ -0,0 +1,11 @@
+(function (exports) { 'use strict';
+
+	var FOO = 'foo';
+
+	console.log( FOO );
+	console.log( FOO );
+	console.log( FOO );
+
+	exports.FOO = FOO;
+
+})((this.myBundle = {}));
diff --git a/test/form/exported-empty-vars/_expected/umd.js b/test/form/exports-at-end-if-possible/_expected/umd.js
similarity index 72%
rename from test/form/exported-empty-vars/_expected/umd.js
rename to test/form/exports-at-end-if-possible/_expected/umd.js
index 9cde4bd..f30f365 100644
--- a/test/form/exported-empty-vars/_expected/umd.js
+++ b/test/form/exports-at-end-if-possible/_expected/umd.js
@@ -4,9 +4,12 @@
 	factory((global.myBundle = {}));
 }(this, function (exports) { 'use strict';
 
-	exports.foo = 42;
+	var FOO = 'foo';
 
-	exports.bar = 43;
-	exports.baz = 44;
+	console.log( FOO );
+	console.log( FOO );
+	console.log( FOO );
+
+	exports.FOO = FOO;
 
 }));
diff --git a/test/form/exports-at-end-if-possible/main.js b/test/form/exports-at-end-if-possible/main.js
new file mode 100644
index 0000000..ee6a75a
--- /dev/null
+++ b/test/form/exports-at-end-if-possible/main.js
@@ -0,0 +1,5 @@
+export var FOO = 'foo';
+
+console.log( FOO );
+console.log( FOO );
+console.log( FOO );
diff --git a/test/form/multiple-exports/_expected/amd.js b/test/form/multiple-exports/_expected/amd.js
index 5460f4f..2ebff3b 100644
--- a/test/form/multiple-exports/_expected/amd.js
+++ b/test/form/multiple-exports/_expected/amd.js
@@ -1,6 +1,9 @@
 define(['exports'], function (exports) { 'use strict';
 
-	exports.foo = 1;
-	exports.bar = 2;
+	var foo = 1;
+	var bar = 2;
+
+	exports.foo = foo;
+	exports.bar = bar;
 
 });
diff --git a/test/form/multiple-exports/_expected/cjs.js b/test/form/multiple-exports/_expected/cjs.js
index 0bbfe60..1968b8b 100644
--- a/test/form/multiple-exports/_expected/cjs.js
+++ b/test/form/multiple-exports/_expected/cjs.js
@@ -1,4 +1,7 @@
 'use strict';
 
-exports.foo = 1;
-exports.bar = 2;
+var foo = 1;
+var bar = 2;
+
+exports.foo = foo;
+exports.bar = bar;
diff --git a/test/form/multiple-exports/_expected/iife.js b/test/form/multiple-exports/_expected/iife.js
index 09461cb..8ed8290 100644
--- a/test/form/multiple-exports/_expected/iife.js
+++ b/test/form/multiple-exports/_expected/iife.js
@@ -1,6 +1,9 @@
 (function (exports) { 'use strict';
 
-	exports.foo = 1;
-	exports.bar = 2;
+	var foo = 1;
+	var bar = 2;
+
+	exports.foo = foo;
+	exports.bar = bar;
 
 })((this.myBundle = {}));
diff --git a/test/form/multiple-exports/_expected/umd.js b/test/form/multiple-exports/_expected/umd.js
index 2fd0eb7..687b75c 100644
--- a/test/form/multiple-exports/_expected/umd.js
+++ b/test/form/multiple-exports/_expected/umd.js
@@ -4,7 +4,10 @@
 	factory((global.myBundle = {}));
 }(this, function (exports) { 'use strict';
 
-	exports.foo = 1;
-	exports.bar = 2;
+	var foo = 1;
+	var bar = 2;
+
+	exports.foo = foo;
+	exports.bar = bar;
 
 }));
diff --git a/test/form/preserves-comments-after-imports/_expected/amd.js b/test/form/preserves-comments-after-imports/_expected/amd.js
index fd4591b..82a0a52 100644
--- a/test/form/preserves-comments-after-imports/_expected/amd.js
+++ b/test/form/preserves-comments-after-imports/_expected/amd.js
@@ -4,6 +4,8 @@ define(['exports'], function (exports) { 'use strict';
 	var number = 5;
 
 	/** A comment for obj */
-	exports.obj = { number };
+	var obj = { number };
+
+	exports.obj = obj;
 
 });
diff --git a/test/form/preserves-comments-after-imports/_expected/cjs.js b/test/form/preserves-comments-after-imports/_expected/cjs.js
index 86e64c1..8b15cd1 100644
--- a/test/form/preserves-comments-after-imports/_expected/cjs.js
+++ b/test/form/preserves-comments-after-imports/_expected/cjs.js
@@ -4,4 +4,6 @@
 var number = 5;
 
 /** A comment for obj */
-exports.obj = { number };
+var obj = { number };
+
+exports.obj = obj;
diff --git a/test/form/preserves-comments-after-imports/_expected/iife.js b/test/form/preserves-comments-after-imports/_expected/iife.js
index 02f5255..9da8252 100644
--- a/test/form/preserves-comments-after-imports/_expected/iife.js
+++ b/test/form/preserves-comments-after-imports/_expected/iife.js
@@ -4,6 +4,8 @@
 	var number = 5;
 
 	/** A comment for obj */
-	exports.obj = { number };
+	var obj = { number };
+
+	exports.obj = obj;
 
 })((this.myBundle = {}));
diff --git a/test/form/preserves-comments-after-imports/_expected/umd.js b/test/form/preserves-comments-after-imports/_expected/umd.js
index 6993070..96fec25 100644
--- a/test/form/preserves-comments-after-imports/_expected/umd.js
+++ b/test/form/preserves-comments-after-imports/_expected/umd.js
@@ -8,6 +8,8 @@
 	var number = 5;
 
 	/** A comment for obj */
-	exports.obj = { number };
+	var obj = { number };
+
+	exports.obj = obj;
 
 }));
diff --git a/test/function/assignment-to-exports/_config.js b/test/function/assignment-to-exports/_config.js
index c958adb..fac0cb3 100644
--- a/test/function/assignment-to-exports/_config.js
+++ b/test/function/assignment-to-exports/_config.js
@@ -6,5 +6,6 @@ module.exports = {
 		assert.equal( exports.count, 0 );
 		exports.incr();
 		assert.equal( exports.count, 1 );
-	}
+	},
+	// solo: true
 };