diff --git a/src/app-layer-modbus.c b/src/app-layer-modbus.c
index 7d23bcacc4..d2518b5313 100644
--- a/src/app-layer-modbus.c
+++ b/src/app-layer-modbus.c
@@ -829,7 +829,7 @@ static int ModbusParseDiagnosticRequest(ModbusTransaction   *tx,
     if (tx->subFunction != MODBUS_SUBFUNC_QUERY_DATA) {
         switch (tx->subFunction) {
             case MODBUS_SUBFUNC_RESTART_COM:
-                if ((data != 0x00) || (data != 0xFF00))
+                if ((data != 0x00) && (data != 0xFF00))
                     goto error;
                 break;