diff --git a/src/finalisers/iife.js b/src/finalisers/iife.js
index 8120594..3946286 100644
--- a/src/finalisers/iife.js
+++ b/src/finalisers/iife.js
@@ -3,16 +3,23 @@ import { getName } from '../utils/map-helpers.js';
 import getInteropBlock from './shared/getInteropBlock.js';
 import getExportBlock from './shared/getExportBlock.js';
 import getGlobalNameMaker from './shared/getGlobalNameMaker.js';
+import propertyStringFor from './shared/propertyStringFor';
+
+// thisProp('foo.bar.baz') === "this['foo']['bar']['baz']"
+const thisProp = propertyStringFor('this');
+
+// propString('foo.bar') === "['foo']['bar']"
+const propString = propertyStringFor('');
 
 function setupNamespace ( keypath ) {
-	const parts = keypath.split( '.' ); // TODO support e.g. `foo['something-hyphenated']`?
+	const parts = keypath.split( '.' );
 
 	parts.pop();
 
 	let acc = 'this';
 
 	return parts
-		.map( part => ( acc += `.${part}`, `${acc} = ${acc} || {};` ) )
+		.map( part => ( acc += propString(part), `${acc} = ${acc} || {};` ) )
 		.join( '\n' ) + '\n';
 }
 
@@ -31,7 +38,7 @@ export default function iife ( bundle, magicString, { exportMode, indentString,
 	}
 
 	if ( exportMode === 'named' ) {
-		dependencies.unshift( `(this.${name} = this.${name} || {})` );
+		dependencies.unshift( `(${thisProp(name)} = ${thisProp(name)} || {})` );
 		args.unshift( 'exports' );
 	}
 
@@ -41,7 +48,7 @@ export default function iife ( bundle, magicString, { exportMode, indentString,
 	const wrapperOutro = `\n\n}(${dependencies}));`;
 
 	if ( exportMode === 'default' ) {
-		wrapperIntro = ( isNamespaced ? `this.` : `${bundle.varOrConst} ` ) + `${name} = ${wrapperIntro}`;
+		wrapperIntro = ( isNamespaced ? thisProp(name) : `${bundle.varOrConst} ${name}` ) + ` = ${wrapperIntro}`;
 	}
 
 	if ( isNamespaced ) {
diff --git a/src/finalisers/shared/propertyStringFor.js b/src/finalisers/shared/propertyStringFor.js
new file mode 100644
index 0000000..f0c2948
--- /dev/null
+++ b/src/finalisers/shared/propertyStringFor.js
@@ -0,0 +1,17 @@
+// Generate strings which dereference dotted properties, but use array notation
+
+const shouldUseDot = /^[a-zA-Z$_][a-zA-Z0-9$_]*$/;
+const dereferenceString = prop =>
+    prop.match(shouldUseDot) ? `.${prop}` : `['${prop}']`;
+
+/**
+ * returns a function which generates property dereference strings for the given name
+ *
+ * const getGlobalProp = propertyStringFor('global');
+ * getGlobalProp('foo.bar.baz') => `global['foo']['bar']['baz']`
+ */
+const propertyStringFor = objName => propName =>
+  objName + propName.split('.').map(dereferenceString).join('');
+
+
+export default propertyStringFor;
\ No newline at end of file
diff --git a/src/finalisers/umd.js b/src/finalisers/umd.js
index 67b9860..6f0541f 100644
--- a/src/finalisers/umd.js
+++ b/src/finalisers/umd.js
@@ -4,6 +4,13 @@ import getInteropBlock from './shared/getInteropBlock.js';
 import getExportBlock from './shared/getExportBlock.js';
 import getGlobalNameMaker from './shared/getGlobalNameMaker.js';
 import esModuleExport from './shared/esModuleExport.js';
+import propertyStringFor from './shared/propertyStringFor.js';
+
+// globalProp('foo.bar') === "global['foo']['bar']"
+const globalProp = propertyStringFor('global');
+
+// propString('foo.bar') === "['foo']['bar']"
+const propString = propertyStringFor('');
 
 function setupNamespace ( name ) {
 	const parts = name.split( '.' );
@@ -11,8 +18,8 @@ function setupNamespace ( name ) {
 
 	let acc = 'global';
 	return parts
-		.map( part => ( acc += `.${part}`, `${acc} = ${acc} || {}` ) )
-		.concat( `global.${name}` )
+		.map( part => ( acc += propString(part), `${acc} = ${acc} || {}` ) )
+		.concat( globalProp(name) )
 		.join( ', ' );
 }
 
@@ -27,14 +34,14 @@ export default function umd ( bundle, magicString, { exportMode, indentString, i
 
 	const amdDeps = bundle.externalModules.map( quotePath );
 	const cjsDeps = bundle.externalModules.map( req );
-	const globalDeps = bundle.externalModules.map( module => `global.${globalNameMaker( module )}` );
+	const globalDeps = bundle.externalModules.map( module => globalProp(globalNameMaker( module )) );
 
 	const args = bundle.externalModules.map( getName );
 
 	if ( exportMode === 'named' ) {
 		amdDeps.unshift( `'exports'` );
 		cjsDeps.unshift( `exports` );
-		globalDeps.unshift( `(${setupNamespace(options.moduleName)} = global.${options.moduleName} || {})` );
+		globalDeps.unshift( `(${setupNamespace(options.moduleName)} = ${globalProp(options.moduleName)} || {})` );
 
 		args.unshift( 'exports' );
 	}
@@ -50,10 +57,10 @@ export default function umd ( bundle, magicString, { exportMode, indentString, i
 
 	const globalExport = options.noConflict === true ?
 		`(function() {
-				var current = global.${options.moduleName};
+				var current = ${globalProp(options.moduleName)};
 				var exports = factory(${globalDeps});
-				global.${options.moduleName} = exports;
-				exports.noConflict = function() { global.${options.moduleName} = current; return exports; };
+				${globalProp(options.moduleName)} = exports;
+				exports.noConflict = function() { ${globalProp(options.moduleName)} = current; return exports; };
 			})()` : `(${defaultExport}factory(${globalDeps}))`;
 
 	const wrapperIntro =
diff --git a/test/form/module-name-scoped-package/_config.js b/test/form/module-name-scoped-package/_config.js
new file mode 100644
index 0000000..5681881
--- /dev/null
+++ b/test/form/module-name-scoped-package/_config.js
@@ -0,0 +1,6 @@
+module.exports = {
+	description: 'allows module name with dashes to be added to the global object',
+	options: {
+		moduleName: '@scoped/npm-package'
+	}
+};
diff --git a/test/form/module-name-scoped-package/_expected/amd.js b/test/form/module-name-scoped-package/_expected/amd.js
new file mode 100644
index 0000000..69586a0
--- /dev/null
+++ b/test/form/module-name-scoped-package/_expected/amd.js
@@ -0,0 +1,9 @@
+define(['exports'], function (exports) { 'use strict';
+
+	let foo = 'foo';
+
+	exports.foo = foo;
+
+	Object.defineProperty(exports, '__esModule', { value: true });
+
+});
diff --git a/test/form/module-name-scoped-package/_expected/cjs.js b/test/form/module-name-scoped-package/_expected/cjs.js
new file mode 100644
index 0000000..796e3ef
--- /dev/null
+++ b/test/form/module-name-scoped-package/_expected/cjs.js
@@ -0,0 +1,7 @@
+'use strict';
+
+Object.defineProperty(exports, '__esModule', { value: true });
+
+let foo = 'foo';
+
+exports.foo = foo;
diff --git a/test/form/module-name-scoped-package/_expected/es.js b/test/form/module-name-scoped-package/_expected/es.js
new file mode 100644
index 0000000..3ee7d0b
--- /dev/null
+++ b/test/form/module-name-scoped-package/_expected/es.js
@@ -0,0 +1,3 @@
+let foo = 'foo';
+
+export { foo };
diff --git a/test/form/module-name-scoped-package/_expected/iife.js b/test/form/module-name-scoped-package/_expected/iife.js
new file mode 100644
index 0000000..7445d49
--- /dev/null
+++ b/test/form/module-name-scoped-package/_expected/iife.js
@@ -0,0 +1,8 @@
+(function (exports) {
+	'use strict';
+
+	let foo = 'foo';
+
+	exports.foo = foo;
+
+}((this['@scoped/npm-package'] = this['@scoped/npm-package'] || {})));
diff --git a/test/form/module-name-scoped-package/_expected/umd.js b/test/form/module-name-scoped-package/_expected/umd.js
new file mode 100644
index 0000000..3382219
--- /dev/null
+++ b/test/form/module-name-scoped-package/_expected/umd.js
@@ -0,0 +1,13 @@
+(function (global, factory) {
+	typeof exports === 'object' && typeof module !== 'undefined' ? factory(exports) :
+	typeof define === 'function' && define.amd ? define(['exports'], factory) :
+	(factory((global['@scoped/npm-package'] = global['@scoped/npm-package'] || {})));
+}(this, (function (exports) { 'use strict';
+
+	let foo = 'foo';
+
+	exports.foo = foo;
+
+	Object.defineProperty(exports, '__esModule', { value: true });
+
+})));
diff --git a/test/form/module-name-scoped-package/main.js b/test/form/module-name-scoped-package/main.js
new file mode 100644
index 0000000..816d625
--- /dev/null
+++ b/test/form/module-name-scoped-package/main.js
@@ -0,0 +1 @@
+export let foo = 'foo';
diff --git a/test/form/module-name-with-dashes/_config.js b/test/form/module-name-with-dashes/_config.js
new file mode 100644
index 0000000..c466b88
--- /dev/null
+++ b/test/form/module-name-with-dashes/_config.js
@@ -0,0 +1,6 @@
+module.exports = {
+	description: 'allows module name with dashes to be added to the global object',
+	options: {
+		moduleName: 'module-name-with-dashes'
+	}
+};
diff --git a/test/form/module-name-with-dashes/_expected/amd.js b/test/form/module-name-with-dashes/_expected/amd.js
new file mode 100644
index 0000000..69586a0
--- /dev/null
+++ b/test/form/module-name-with-dashes/_expected/amd.js
@@ -0,0 +1,9 @@
+define(['exports'], function (exports) { 'use strict';
+
+	let foo = 'foo';
+
+	exports.foo = foo;
+
+	Object.defineProperty(exports, '__esModule', { value: true });
+
+});
diff --git a/test/form/module-name-with-dashes/_expected/cjs.js b/test/form/module-name-with-dashes/_expected/cjs.js
new file mode 100644
index 0000000..796e3ef
--- /dev/null
+++ b/test/form/module-name-with-dashes/_expected/cjs.js
@@ -0,0 +1,7 @@
+'use strict';
+
+Object.defineProperty(exports, '__esModule', { value: true });
+
+let foo = 'foo';
+
+exports.foo = foo;
diff --git a/test/form/module-name-with-dashes/_expected/es.js b/test/form/module-name-with-dashes/_expected/es.js
new file mode 100644
index 0000000..3ee7d0b
--- /dev/null
+++ b/test/form/module-name-with-dashes/_expected/es.js
@@ -0,0 +1,3 @@
+let foo = 'foo';
+
+export { foo };
diff --git a/test/form/module-name-with-dashes/_expected/iife.js b/test/form/module-name-with-dashes/_expected/iife.js
new file mode 100644
index 0000000..5eb1062
--- /dev/null
+++ b/test/form/module-name-with-dashes/_expected/iife.js
@@ -0,0 +1,8 @@
+(function (exports) {
+	'use strict';
+
+	let foo = 'foo';
+
+	exports.foo = foo;
+
+}((this['module-name-with-dashes'] = this['module-name-with-dashes'] || {})));
diff --git a/test/form/module-name-with-dashes/_expected/umd.js b/test/form/module-name-with-dashes/_expected/umd.js
new file mode 100644
index 0000000..8d90ff6
--- /dev/null
+++ b/test/form/module-name-with-dashes/_expected/umd.js
@@ -0,0 +1,13 @@
+(function (global, factory) {
+	typeof exports === 'object' && typeof module !== 'undefined' ? factory(exports) :
+	typeof define === 'function' && define.amd ? define(['exports'], factory) :
+	(factory((global['module-name-with-dashes'] = global['module-name-with-dashes'] || {})));
+}(this, (function (exports) { 'use strict';
+
+	let foo = 'foo';
+
+	exports.foo = foo;
+
+	Object.defineProperty(exports, '__esModule', { value: true });
+
+})));
diff --git a/test/form/module-name-with-dashes/main.js b/test/form/module-name-with-dashes/main.js
new file mode 100644
index 0000000..816d625
--- /dev/null
+++ b/test/form/module-name-with-dashes/main.js
@@ -0,0 +1 @@
+export let foo = 'foo';