diff --git a/src/regexp_nfa.c b/src/regexp_nfa.c
index 2bd75af..3d125f0 100644
--- a/src/regexp_nfa.c
+++ b/src/regexp_nfa.c
@@ -5408,7 +5408,7 @@
     regsubs_T		*m;
 {
     int		result;
-    int		size = 0;
+    size_t	size = 0;
     int		flag = 0;
     int		go_to_nextline = FALSE;
     nfa_thread_T *t;