diff --git a/mysql-test/lib/mtr_cases.pm b/mysql-test/lib/mtr_cases.pm
index 4d6885f5495..6ec73715a0c 100644
--- a/mysql-test/lib/mtr_cases.pm
+++ b/mysql-test/lib/mtr_cases.pm
@@ -971,7 +971,7 @@ sub envsubst {
 
   if ( ! defined $ENV{$string} )
   {
-    mtr_error("opt file referense \$$string that is unknown");
+    mtr_error(".opt file references '$string' which is not set");
   }
 
   return $ENV{$string};