diff --git a/src/common.c b/src/common.c
index a9166bf9..14bf7f98 100644
--- a/src/common.c
+++ b/src/common.c
@@ -241,12 +241,12 @@ gboolean valid_phone_number_format(const char *number)
 	if (!len)
 		return FALSE;
 
-	if (len > OFONO_MAX_PHONE_NUMBER_LENGTH)
-		return FALSE;
-
 	if (number[0] == '+')
 		begin = 1;
 
+	if ((len - begin) > OFONO_MAX_PHONE_NUMBER_LENGTH)
+		return FALSE;
+
 	for (i = begin; i < len; i++) {
 		if (number[i] >= '0' && number[i] <= '9')
 			continue;