diff --git a/src/finalisers/umd.js b/src/finalisers/umd.js
index 0a93e03..5144a8e 100644
--- a/src/finalisers/umd.js
+++ b/src/finalisers/umd.js
@@ -78,7 +78,7 @@ export default function umd ( bundle, magicString, { exportMode, indentString, i
 			${globalExport};
 		}(this, (function (${args}) {${useStrict}
 
-		`.replace( /^\t\t/gm, '' ).replace( /^\t/gm, magicString.getIndentString() );
+		`.replace( /^\t\t/gm, '' ).replace( /^\t/gm, indentString || '\t' );
 
 	// var foo__default = 'default' in foo ? foo['default'] : foo;
 	const interopBlock = getInteropBlock( bundle, options );
diff --git a/test/form/indent-false/_expected/amd.js b/test/form/indent-false/_expected/amd.js
index 07c823c..2ef21fb 100644
--- a/test/form/indent-false/_expected/amd.js
+++ b/test/form/indent-false/_expected/amd.js
@@ -1,7 +1,7 @@
 define(function () { 'use strict';
 
 function foo () {
-	console.log( 'indented with tabs' );
+	console.log( 'not indented' );
 }
 
 return foo;
diff --git a/test/form/indent-false/_expected/cjs.js b/test/form/indent-false/_expected/cjs.js
index 7f6e0b9..04d1ea3 100644
--- a/test/form/indent-false/_expected/cjs.js
+++ b/test/form/indent-false/_expected/cjs.js
@@ -1,7 +1,7 @@
 'use strict';
 
 function foo () {
-	console.log( 'indented with tabs' );
+	console.log( 'not indented' );
 }
 
 module.exports = foo;
diff --git a/test/form/indent-false/_expected/es.js b/test/form/indent-false/_expected/es.js
index d4b23ef..2710c80 100644
--- a/test/form/indent-false/_expected/es.js
+++ b/test/form/indent-false/_expected/es.js
@@ -1,5 +1,5 @@
 function foo () {
-	console.log( 'indented with tabs' );
+	console.log( 'not indented' );
 }
 
 export default foo;
diff --git a/test/form/indent-false/_expected/iife.js b/test/form/indent-false/_expected/iife.js
index 54ba717..0b46c84 100644
--- a/test/form/indent-false/_expected/iife.js
+++ b/test/form/indent-false/_expected/iife.js
@@ -2,7 +2,7 @@ var foo = (function () {
 'use strict';
 
 function foo () {
-	console.log( 'indented with tabs' );
+	console.log( 'not indented' );
 }
 
 return foo;
diff --git a/test/form/indent-false/_expected/umd.js b/test/form/indent-false/_expected/umd.js
index c0289b0..22e4c7d 100644
--- a/test/form/indent-false/_expected/umd.js
+++ b/test/form/indent-false/_expected/umd.js
@@ -5,9 +5,9 @@
 }(this, (function () { 'use strict';
 
 function foo () {
-	console.log( 'indented with tabs' );
+	console.log( 'not indented' );
 }
 
 return foo;
 
-})));
\ No newline at end of file
+})));
diff --git a/test/form/indent-false/main.js b/test/form/indent-false/main.js
index 10005f9..e68e7b3 100644
--- a/test/form/indent-false/main.js
+++ b/test/form/indent-false/main.js
@@ -1,3 +1,3 @@
 export default function foo () {
-	console.log( 'indented with tabs' );
+	console.log( 'not indented' );
 }
diff --git a/test/form/indent-spaces/_config.js b/test/form/indent-spaces/_config.js
new file mode 100644
index 0000000..d684967
--- /dev/null
+++ b/test/form/indent-spaces/_config.js
@@ -0,0 +1,7 @@
+module.exports = {
+	description: 'auto-indents with indent: true',
+	options: {
+		moduleName: 'foo',
+		indent: '  '
+	}
+};
diff --git a/test/form/indent-spaces/_expected/amd.js b/test/form/indent-spaces/_expected/amd.js
new file mode 100644
index 0000000..445c02f
--- /dev/null
+++ b/test/form/indent-spaces/_expected/amd.js
@@ -0,0 +1,9 @@
+define(function () { 'use strict';
+
+  function foo () {
+  	console.log( 'indented with tabs' );
+  }
+
+  return foo;
+
+});
diff --git a/test/form/indent-spaces/_expected/cjs.js b/test/form/indent-spaces/_expected/cjs.js
new file mode 100644
index 0000000..7f6e0b9
--- /dev/null
+++ b/test/form/indent-spaces/_expected/cjs.js
@@ -0,0 +1,7 @@
+'use strict';
+
+function foo () {
+	console.log( 'indented with tabs' );
+}
+
+module.exports = foo;
diff --git a/test/form/indent-spaces/_expected/es.js b/test/form/indent-spaces/_expected/es.js
new file mode 100644
index 0000000..d4b23ef
--- /dev/null
+++ b/test/form/indent-spaces/_expected/es.js
@@ -0,0 +1,5 @@
+function foo () {
+	console.log( 'indented with tabs' );
+}
+
+export default foo;
diff --git a/test/form/indent-spaces/_expected/iife.js b/test/form/indent-spaces/_expected/iife.js
new file mode 100644
index 0000000..f83141c
--- /dev/null
+++ b/test/form/indent-spaces/_expected/iife.js
@@ -0,0 +1,10 @@
+var foo = (function () {
+  'use strict';
+
+  function foo () {
+  	console.log( 'indented with tabs' );
+  }
+
+  return foo;
+
+}());
diff --git a/test/form/indent-spaces/_expected/umd.js b/test/form/indent-spaces/_expected/umd.js
new file mode 100644
index 0000000..86fd887
--- /dev/null
+++ b/test/form/indent-spaces/_expected/umd.js
@@ -0,0 +1,13 @@
+(function (global, factory) {
+  typeof exports === 'object' && typeof module !== 'undefined' ? module.exports = factory() :
+  typeof define === 'function' && define.amd ? define(factory) :
+  (global.foo = factory());
+}(this, (function () { 'use strict';
+
+  function foo () {
+  	console.log( 'indented with tabs' );
+  }
+
+  return foo;
+
+})));
diff --git a/test/form/indent-spaces/main.js b/test/form/indent-spaces/main.js
new file mode 100644
index 0000000..10005f9
--- /dev/null
+++ b/test/form/indent-spaces/main.js
@@ -0,0 +1,3 @@
+export default function foo () {
+	console.log( 'indented with tabs' );
+}