diff --git a/m4/prog-cc-c-o.m4 b/m4/prog-cc-c-o.m4
index a31a4a414..fe388203d 100644
--- a/m4/prog-cc-c-o.m4
+++ b/m4/prog-cc-c-o.m4
@@ -31,7 +31,7 @@ AC_CACHE_CHECK(
       break
     fi
   done
-  rm -f core conftest*
+  rm -rf core conftest*
   unset am_i])
 if test "$am_cv_prog_cc_c_o" != yes; then
    # Losing compiler, so override with the script.
