diff --git a/configure b/configure
index e2a558aba8eeb9bbc6ec79fdce14260372303829..443525b240231e6983db26a1f617c4fa1efa17ba 100755
--- a/configure
+++ b/configure
@@ -604,6 +604,9 @@ sub secondary_variables
             $precomp_use_flags='';
         }
     }
+    $precomp_file //= '';
+    $precomp_build_flags //= '';
+    $precomp_use_flags //= '';
     
 
     my $nativecheck = $cflags=~/-mtune=native/ ? ' (using native flag for -mcpu and -mtune)' :'';