diff --git a/src/tools/PerfectHash.pm b/src/tools/PerfectHash.pm
index bd339e38a2..54f5d4e994 100644
--- a/src/tools/PerfectHash.pm
+++ b/src/tools/PerfectHash.pm
@@ -131,7 +131,7 @@ sub generate_hash_function
 	}
 	$f .= sprintf "\n" if ($nhash % 8 != 0);
 	$f .= sprintf "\t};\n\n";
-	$f .= sprintf "\tconst unsigned char *k = key;\n";
+	$f .= sprintf "\tconst unsigned char *k = (const unsigned char *) key;\n";
 	$f .= sprintf "\tsize_t\t\tkeylen = %d;\n", $options{fixed_key_length}
 	  if (defined $options{fixed_key_length});
 	$f .= sprintf "\tuint32\t\ta = %d;\n",   $hash_seed1;