diff --git a/wercker.yml b/wercker.yml
index 2736e2c113..7e3d47a2b3 100644
--- a/wercker.yml
+++ b/wercker.yml
@@ -29,7 +29,7 @@ mjit-test1:
           cat <<'EOS' > /usr/local/bin/mjit-debug-on-fail
           #!/bin/bash
           if ! "$@"; then
-            for f in $(find /tmp -type f -name "ruby_mjit*.c"); do
+            for f in $(find /tmp -type f -name "_ruby_mjit*.c"); do
               echo "[${f}]==="
               cat "$f"
               echo "==="