diff --git a/src/common.c b/src/common.c
index 4dcbc835..f955a768 100644
--- a/src/common.c
+++ b/src/common.c
@@ -709,7 +709,7 @@ const char *registration_tech_to_string(int tech)
 gboolean is_valid_apn(const char *apn)
 {
 	int i;
-	int last_period = 0;
+	int last_period = -1;
 
 	if (apn == NULL)
 		return FALSE;