diff --git a/doh-server/server.go b/doh-server/server.go
index 79e2a23..85ea36f 100644
--- a/doh-server/server.go
+++ b/doh-server/server.go
@@ -129,6 +129,9 @@ func (s *Server) handlerFunc(w http.ResponseWriter, r *http.Request) {
 	}
 
 	ednsClientSubnet := r.FormValue("edns_client_subnet")
+	if ednsClientSubnet == "0/0" {
+		ednsClientSubnet = "0.0.0.0/0"
+	}
 	ednsClientFamily := uint16(0)
 	ednsClientAddress := net.IP(nil)
 	ednsClientNetmask := uint8(255)