diff --git a/src/common.c b/src/common.c
index fcb9742..8ec6646 100644
--- a/src/common.c
+++ b/src/common.c
@@ -1417,6 +1417,15 @@ set_boolean_if_valid (bool *out, const char *s)
 	return true;
 }
 
+static bool
+xstrtoul (unsigned long *out, const char *s, int base)
+{
+	char *end;
+	errno = 0;
+	*out = strtoul (s, &end, base);
+	return errno == 0 && !*end && end != s;
+}
+
 static bool
 read_line (FILE *fp, struct str *s)
 {
diff --git a/src/zyklonb.c b/src/zyklonb.c
index a57b8c4..3d8d388 100644
--- a/src/zyklonb.c
+++ b/src/zyklonb.c
@@ -1418,10 +1418,8 @@ irc_try_reconnect (struct bot_context *ctx)
 	const char *delay_str = str_map_find (&ctx->config, "reconnect_delay");
 	hard_assert (delay_str != NULL);  // We have a default value for this
 
-	char *end_ptr;
-	errno = 0;
-	long delay = strtol (delay_str, &end_ptr, 10);
-	if (errno != 0 || end_ptr == delay_str || *end_ptr)
+	unsigned long delay;
+	if (!xstrtoul (&delay, delay_str, 10))
 	{
 		print_error ("invalid configuration value for `%s'",
 			"reconnect_delay");