diff --git a/packages/@angular/cli/bin/ng b/packages/@angular/cli/bin/ng
index 85d52dfbc60e..dfd042cb0872 100755
--- a/packages/@angular/cli/bin/ng
+++ b/packages/@angular/cli/bin/ng
@@ -155,13 +155,21 @@ resolve('@angular/cli', { basedir: process.cwd() },
       }
 
       if (shouldWarn && CliConfig.fromGlobal().get('warnings.versionMismatch')) {
-        // eslint-disable no-console
-        console.log(yellow(stripIndents`
-          Your global Angular CLI version (${globalVersion}) is greater than your local
-          version (${localVersion}). The local Angular CLI version is used.
-
-          To disable this warning use "ng set --global warnings.versionMismatch=false".
-        `));
+        let warning = yellow(stripIndents`
+        Your global Angular CLI version (${globalVersion}) is greater than your local
+        version (${localVersion}). The local Angular CLI version is used.
+
+        To disable this warning use "ng set --global warnings.versionMismatch=false".
+        `);
+        // Don't show warning colorised on `ng completion`
+         if (process.argv[2] !== 'completion') {
+           // eslint-disable no-console
+           console.log(warning);
+         } else {
+           // eslint-disable no-console
+           console.error(warning);
+           process.exit(1);
+         }
       }
 
       // No error implies a projectLocalCli, which will load whatever