diff --git a/lib/isc/httpd.c b/lib/isc/httpd.c
index 18fecf1c6e..809cb30728 100644
--- a/lib/isc/httpd.c
+++ b/lib/isc/httpd.c
@@ -425,9 +425,8 @@ process_request(isc_httpd_t *httpd, size_t last_len) {
 
 		if (name_match(header, "Content-Length")) {
 			char *endptr;
-			long val = strtol(header->value, &endptr, 10);
-
 			errno = 0;
+			long val = strtol(header->value, &endptr, 10);
 
 			/* ensure we consumed all digits */
 			if ((header->value + header->value_len) != endptr) {