diff --git a/rtl/unix/cthreads.pp b/rtl/unix/cthreads.pp
index 3bc7e5a214..e65d4caffe 100644
--- a/rtl/unix/cthreads.pp
+++ b/rtl/unix/cthreads.pp
@@ -463,7 +463,7 @@ Type  PINTRTLEvent = ^TINTRTLEvent;
             res := pthread_mutex_init(@CS,@MAttr)
           else
             { No recursive mutex support :/ }
-            res := pthread_mutex_init(@CS,NIL);
+            fpc_threaderror
         end
       else
         res:= pthread_mutex_init(@CS,NIL);