diff --git a/net/nat/ipv4_nat.c b/net/nat/ipv4_nat.c
index ffb71d442be..51145362bf0 100644
--- a/net/nat/ipv4_nat.c
+++ b/net/nat/ipv4_nat.c
@@ -795,6 +795,7 @@ int ipv4_nat_outbound(FAR struct net_driver_s *dev,
         {
           /* Outbound entry creation failed, should have entry. */
 
+          nat_unlock();
           return -ENOENT;
         }
     }
diff --git a/net/nat/ipv6_nat.c b/net/nat/ipv6_nat.c
index 8348dbe7d6d..19854008a24 100644
--- a/net/nat/ipv6_nat.c
+++ b/net/nat/ipv6_nat.c
@@ -683,6 +683,7 @@ int ipv6_nat_outbound(FAR struct net_driver_s *dev,
         {
           /* Outbound entry creation failed, should have entry. */
 
+          nat_unlock();
           return -ENOENT;
         }
     }