diff --git a/p2p/nat/nat.go b/p2p/nat/nat.go
index 879b69c06d9815bae86499f0a632bb849ae2f77a..3a4ae60b4d35a1f0d68ea03a65195b8738478df2 100644
--- a/p2p/nat/nat.go
+++ b/p2p/nat/nat.go
@@ -177,7 +177,7 @@ func (nat *NAT) establishMapping(m *mapping) {
 		// Some hardware does not support mappings with timeout, so try that
 		newport, err = nat.nat.AddPortMapping(m.Protocol(), m.InternalPort(), comment, 0)
 	}
-	nat.natmu.Lock()
+	nat.natmu.Unlock()
 
 	failure := func() {
 		m.setExternalPort(0) // clear mapping