diff --git a/maintner/netsource.go b/maintner/netsource.go
index 5c4d28f..356743f 100644
--- a/maintner/netsource.go
+++ b/maintner/netsource.go
@@ -74,6 +74,9 @@
 // isNoInternetError reports whether the provided error is because there's no
 // network connectivity.
 func isNoInternetError(err error) bool {
+	if err == nil {
+		return false
+	}
 	switch err := err.(type) {
 	case *url.Error:
 		return isNoInternetError(err.Err)