diff --git a/src/app-layer-protos.c b/src/app-layer-protos.c
index fd87412571..1abf295e18 100644
--- a/src/app-layer-protos.c
+++ b/src/app-layer-protos.c
@@ -71,6 +71,9 @@ const char *AppProtoToString(AppProto alproto)
         case ALPROTO_DNS:
             proto_name = "dns";
             break;
+        case ALPROTO_MODBUS:
+            proto_name = "modbus";
+            break;
         case ALPROTO_FAILED:
 #ifdef UNITTESTS
         case ALPROTO_TEST: