diff --git a/src/utils/identifierHelpers.ts b/src/utils/identifierHelpers.ts
index 3b603eb1a31..38463f07be5 100644
--- a/src/utils/identifierHelpers.ts
+++ b/src/utils/identifierHelpers.ts
@@ -24,5 +24,5 @@ export function makeLegal(str: string): string {
 
 	if (startsWithDigit(str) || blacklisted[str]) str = `_${str}`;
 
-	return str;
+	return str || '_';
 }
diff --git a/test/function/samples/avoid-variable-be-empty/_config.js b/test/function/samples/avoid-variable-be-empty/_config.js
new file mode 100644
index 00000000000..9571570ca02
--- /dev/null
+++ b/test/function/samples/avoid-variable-be-empty/_config.js
@@ -0,0 +1,19 @@
+module.exports = {
+	description: 'avoid variable from empty module name be empty',
+	options: {
+		input: '',
+		plugins: [
+			{
+				resolveId (importee) {
+					return '';
+				},
+				load (path) {
+					return 'export default 0;';
+				},
+			}
+		],
+		output: {
+			format: 'cjs'
+		}
+	}
+};