diff --git a/server.go b/server.go
index 7aa39168..46949ba8 100644
--- a/server.go
+++ b/server.go
@@ -218,9 +218,9 @@ func (mux *ServeMux) HandleRemove(pattern string) {
 	if pattern == "" {
 		panic("dns: invalid pattern " + pattern)
 	}
-	mux.m.Lock()
+	// don't need a mutex here, because deleting is OK, even if the
+	// entry is note there.
 	delete(mux.z, Fqdn(pattern))
-	mux.m.Unlock()
 }
 
 // ServeDNS dispatches the request to the handler whose