--- a/PsychSourceGL/Source/striplibsfrommexfile.m
+++ b/PsychSourceGL/Source/striplibsfrommexfile.m
@@ -96,7 +96,8 @@ if exist(filename, 'file')
 
     fprintf('MEX file %s stripped from superfluous libraries.\n', filename);
 else
-    fprintf('WARNING! MEX file %s does not exist! Can''t strip it!\n', filename);
+    fprintf('ERROR! MEX file %s does not exist! Can''t strip it!\n', filename);
+    exit(1);
 end
 
 return
