diff --git a/src/getchar.c b/src/getchar.c
index f2f3885..a6644d8 100644
--- a/src/getchar.c
+++ b/src/getchar.c
@@ -1001,6 +1001,8 @@
     }
     else
     {
+	int extra;
+
 	/*
 	 * Need to allocate a new buffer.
 	 * In typebuf.tb_buf there must always be room for 3 * (MAXMAPLEN + 4)
@@ -1008,13 +1010,15 @@
 	 * often.
 	 */
 	newoff = MAXMAPLEN + 4;
-	newlen = typebuf.tb_len + addlen + newoff + 4 * (MAXMAPLEN + 4);
-	if (newlen < 0)		    // string is getting too long
+	extra = addlen + newoff + 4 * (MAXMAPLEN + 4);
+	if (typebuf.tb_len > 2147483647 - extra)
 	{
+	    // string is getting too long for a 32 bit int
 	    emsg(_(e_toocompl));    // also calls flush_buffers
 	    setcursor();
 	    return FAIL;
 	}
+	newlen = typebuf.tb_len + extra;
 	s1 = alloc(newlen);
 	if (s1 == NULL)		    // out of memory
 	    return FAIL;