diff --git a/packages/material-ui/src/styles/cssUtils.js b/packages/material-ui/src/styles/cssUtils.js
index 69036c3198ac3b..7d81edfaba9e12 100644
--- a/packages/material-ui/src/styles/cssUtils.js
+++ b/packages/material-ui/src/styles/cssUtils.js
@@ -33,7 +33,6 @@ export function convertLength(baseFontSize) {
         pxLength = toUnitless(length) * toUnitless(baseFontSize);
       } else if (fromUnit === 'rem') {
         pxLength = toUnitless(length) * toUnitless(baseFontSize);
-        return length;
       }
     }
 
diff --git a/packages/material-ui/src/styles/cssUtils.test.js b/packages/material-ui/src/styles/cssUtils.test.js
index f8f9f4510fa81f..a013ff9b9f5ef7 100644
--- a/packages/material-ui/src/styles/cssUtils.test.js
+++ b/packages/material-ui/src/styles/cssUtils.test.js
@@ -41,6 +41,7 @@ describe('cssUtils', () => {
     it('should work as expected', () => {
       const convert = convertLength('16px');
       expect(convert('32px', 'rem')).to.equal('2rem');
+      expect(convert('2rem', 'px')).to.equal('32px');
     });
   });