diff --git a/src/material/schematics/ng-update/index.ts b/src/material/schematics/ng-update/index.ts
index 18644fe90a00..b76c9f98966b 100644
--- a/src/material/schematics/ng-update/index.ts
+++ b/src/material/schematics/ng-update/index.ts
@@ -59,7 +59,9 @@ function renameMdcTokens(): Rule {
       if (shouldRenameTokens(path)) {
         const content = tree.readText(path);
         const updatedContent = content.replace('--mdc-', '--mat-');
-        tree.overwrite(path, updatedContent);
+        if (content !== updatedContent) {
+          tree.overwrite(path, updatedContent);
+        }
       }
     });
   };