diff --git a/src/ExternalModule.js b/src/ExternalModule.js
index 45af687..d6c003d 100644
--- a/src/ExternalModule.js
+++ b/src/ExternalModule.js
@@ -39,7 +39,10 @@ export default class ExternalModule {
 					originalName: name,
 					name,
 
-					module: this
+					module: this,
+					mark: () => {
+						this.importedByBundle[ name ] = true;
+					}
 				});
 			}
 
@@ -47,5 +50,9 @@ export default class ExternalModule {
 		};
 	}
 
-	markExport () {}
+	// External modules are always marked for inclusion in the bundle.
+	// Marking an external module signals its use as a namespace.
+	mark () {
+		this.needsAll = true;
+	}
 }
diff --git a/src/Module.js b/src/Module.js
index f606c6a..eb1501d 100644
--- a/src/Module.js
+++ b/src/Module.js
@@ -144,10 +144,14 @@ export default class Module {
 
 			// Always define a new `Identifier` for the default export.
 			this.exports.define( 'default', {
-				originalName: name,
+				originalName: 'default',
 				name,
 
 				module: this,
+				mark () {
+					this.isUsed = true;
+					this.statement.mark();
+				},
 				statement,
 
 				// Keep the identifier name, if one exists.
@@ -194,6 +198,10 @@ export default class Module {
 					name,
 
 					module: this,
+					mark () {
+						this.isUsed = true;
+						this.statement.mark();
+					},
 					statement,
 					localName: name,
 					expression: declaration
@@ -259,7 +267,11 @@ export default class Module {
 					name,
 
 					statement,
-					module: this
+					module: this,
+					mark () {
+						this.isUsed = true;
+						this.statement.mark();
+					}
 				});
 			});
 
@@ -296,7 +308,11 @@ export default class Module {
 				// For each name we depend on that isn't in scope,
 				// add a new global and bind the local name to it.
 				if ( !this.locals.inScope( name ) ) {
-					this.bundle.globals.define( name );
+					this.bundle.globals.define( name, {
+						originalName: name,
+						name,
+						mark () {}
+					});
 					this.locals.bind( name, this.bundle.globals.reference( name ) );
 				}
 			});
@@ -383,6 +399,8 @@ export default class Module {
 
 	// Enforce dynamic access of the module's properties.
 	dynamicAccess () {
+		if ( this.needsDynamicAccess ) return;
+
 		this.needsDynamicAccess = true;
 		this.markAllExportStatements();
 
@@ -395,20 +413,8 @@ export default class Module {
 		return this.bundle.moduleById[ this.resolvedIds[ source ] ];
 	}
 
-	mark ( name ) {
-		const id = this.locals.lookup( name );
-
-		if ( id && id.module ) {
-			if ( id.module.isExternal ) {
-				id.module.importedByBundle[ id.originalName ] = true;
-			}
-
-			if ( id.statement ) {
-				// Assert that statement is defined. It isn't for external modules.
-				id.isUsed = true;
-				id.statement.mark();
-			}
-		}
+	mark () {
+		this.dynamicAccess();
 	}
 
 	markAllStatements ( isEntryModule ) {
@@ -436,7 +442,7 @@ export default class Module {
 			else {
 				// Be sure to mark the default export for the entry module.
 				if ( isEntryModule && statement.node.type === 'ExportDefaultDeclaration' ) {
-					this.markExport( 'default', this );
+					this.exports.lookup( 'default' ).mark();
 				}
 
 				statement.mark();
@@ -450,34 +456,6 @@ export default class Module {
 		});
 	}
 
-	markExport ( name, importer ) {
-		const id = this.exports.lookup( name );
-
-		if ( id ) {
-			id.isUsed = true;
-
-			// Assert that statement is defined. It isn't for external modules.
-			if ( id.statement ) id.statement.mark();
-
-			return;
-		}
-
-		for ( const module of this.exportAlls ) {
-			const id = module.exports.lookup( name );
-
-			if ( id ) {
-				id.isUsed = true;
-
-				// Assert that statement is defined. It isn't for external modules.
-				if ( id.statement ) id.statement.mark();
-
-				return;
-			}
-		}
-
-		throw new Error( `Module ${this.id} does not export ${name} (imported by ${importer.id})` );
-	}
-
 	parse ( ast ) {
 		// The ast can be supplied programmatically (but usually won't be)
 		if ( !ast ) {
diff --git a/src/Statement.js b/src/Statement.js
index 818b837..1b746ea 100644
--- a/src/Statement.js
+++ b/src/Statement.js
@@ -151,6 +151,7 @@ export default class Statement {
 
 					if ( node._scope ) scope = scope.parent;
 
+					// Optimize namespace lookups, which manifests as MemberExpressions.
 					if ( node.type === 'MemberExpression' && ( !currentMemberExpression || node.object === currentMemberExpression ) ) {
 						currentMemberExpression = node;
 
@@ -162,9 +163,20 @@ export default class Statement {
 							namespace = id;
 						}
 
-						const name = node.property.name || ( node.property.type === 'Literal' ? node.property.value : null );
-
-						if ( !name ) {
+						// Extract the name of the accessed property, from and Identifier or Literal.
+						// Any eventual Literal value is converted to a string.
+						const name = node.property.name ||
+							( node.property.type === 'Literal' ? String( node.property.value ) : null );
+
+						// If we can't resolve the name being accessed,
+						// we require the namespace to be dynamically accessible.
+						//
+						//     // resolvable
+						//     console.log( javascript.keywords[ 6 ] )
+						//
+						//     // unresolvable
+						//     console.log( javascript.keywords[ 1 + 5 ] )
+						if ( name === null ) {
 							namespace.dynamicAccess();
 
 							namespace = null;
@@ -312,31 +324,21 @@ export default class Statement {
 
 		// `export { name } from './other'` is a special case
 		if ( this.isReexportDeclaration ) {
-			const otherModule = this.module.getModule( this.node.source.value );
-
+			// TODO: If we add the specifiers to `dependantIds`,
+			// we can remove this special case.
 			this.node.specifiers.forEach( specifier => {
-				otherModule.markExport( specifier.local.name, this.module );
+				this.module.exports.lookup( specifier.exported.name ).mark();
 			});
 
 			return;
 		}
 
-		this.dependantIds.forEach( id => {
-			// FIXME: what should be done about modules?
-			if ( id.isModule ) {
-				if ( id.isExternal ) {
-
-				} else {
-
-				}
-			}
-
-			id.module && id.module.markExport( id.originalName, this.module );
-		});
+		this.dependantIds.forEach( id => id.mark() );
 
+		// TODO: perhaps these could also be added?
 		keys( this.dependsOn ).forEach( name => {
 			if ( this.defines[ name ] ) return; // TODO maybe exclude from `this.dependsOn` in the first place?
-			this.module.mark( name );
+			this.module.locals.lookup( name ).mark();
 		});
 	}