diff --git a/src/eval.c b/src/eval.c
index 2d2ad1b..d12708e 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -5392,7 +5392,7 @@
     if (start_byte < 0)
 	start_byte = 0; // first index very negative: use zero
     if (last == -1)
-	end_byte = slen;
+	end_byte = (long)slen;
     else
     {
 	end_byte = char_idx2byte(str, slen, last);