diff --git a/src/gui_index.c b/src/gui_index.c
index 2cc8e8db..13be77d5 100644
--- a/src/gui_index.c
+++ b/src/gui_index.c
@@ -540,6 +540,7 @@ static void delete_gui_tempdir(char *tmpdir)
 {
 	char *path;
 	int i;
+	size_t pathlen;
 
 	/* List of files which it's safe to delete */
 	char *files[] = {"gmon.out", "mosflm.lp", "SUMMARY", "XDS.INP",
@@ -552,11 +553,12 @@ static void delete_gui_tempdir(char *tmpdir)
 
 	if ( tmpdir == NULL ) return;
 
-	path = calloc(strlen(tmpdir)+64, 1);
+	pathlen = strlen(tmpdir)+64;
+	path = calloc(pathlen, 1);
 	if ( path == NULL ) return;
 
 	for ( i=0; i<n_files; i++ ) {
-		snprintf(path, 127, "%s/%s", tmpdir, files[i]);
+		snprintf(path, pathlen, "%s/%s", tmpdir, files[i]);
 		unlink(path);
 	}