diff --git a/src/nm-ip4-config.c b/src/nm-ip4-config.c
index 87da7c7545..e23e364578 100644
--- a/src/nm-ip4-config.c
+++ b/src/nm-ip4-config.c
@@ -616,7 +616,7 @@ nm_ip4_config_merge (NMIP4Config *dst, const NMIP4Config *src)
 
 	if (dst_priv->route_metric == -1)
 		dst_priv->route_metric = src_priv->route_metric;
-	else
+	else if (src_priv->route_metric != -1)
 		dst_priv->route_metric = MIN (dst_priv->route_metric, src_priv->route_metric);
 
 	/* domains */
diff --git a/src/nm-ip6-config.c b/src/nm-ip6-config.c
index 4794a0ae38..1cedff5f5d 100644
--- a/src/nm-ip6-config.c
+++ b/src/nm-ip6-config.c
@@ -694,7 +694,7 @@ nm_ip6_config_merge (NMIP6Config *dst, const NMIP6Config *src)
 
 	if (dst_priv->route_metric == -1)
 		dst_priv->route_metric = src_priv->route_metric;
-	else
+	else if (src_priv->route_metric != -1)
 		dst_priv->route_metric = MIN (dst_priv->route_metric, src_priv->route_metric);
 
 	/* domains */