diff --git a/index.ts b/index.ts
index 1b19972..4a0e94f 100644
--- a/index.ts
+++ b/index.ts
@@ -172,6 +172,10 @@ function isNodeKindStringLiteral(value: ts.Node): value is ts.StringLiteral {
 	return value && value.kind === ts.SyntaxKind.StringLiteral;
 }
 
+function isNodeKindIdentifier(value: ts.Node): value is ts.Identifier {
+	return value && value.kind === ts.SyntaxKind.Identifier;
+}
+
 function isNodeKindExportDeclaration(value: ts.Node): value is ts.ExportDeclaration {
 	return value && value.kind === ts.SyntaxKind.ExportDeclaration;
 }
@@ -327,7 +331,7 @@ export default function generate(options: Options): Promise<void> {
 			processTree(sourceFile, function (node) {
 				if (isNodeKindModuleDeclaration(node)) {
 					const name = node.name;
-					if (isNodeKindStringLiteral(name)) {
+					if (isNodeKindStringLiteral(name) || isNodeKindIdentifier(name)) {
 						declaredExternalModules.push(name.text);
 					}
 				}