diff --git a/dbms/src/Processors/Formats/IInputFormat.h b/dbms/src/Processors/Formats/IInputFormat.h
index 7a12f1a073b..0e96b106303 100644
--- a/dbms/src/Processors/Formats/IInputFormat.h
+++ b/dbms/src/Processors/Formats/IInputFormat.h
@@ -13,7 +13,7 @@ class ReadBuffer;
 class IInputFormat : public ISource
 {
 private:
-    ReadBuffer & in;
+    ReadBuffer & in [[maybe_unused]];
 
 public:
     IInputFormat(Block header, ReadBuffer & in)
diff --git a/dbms/src/Processors/Port.h b/dbms/src/Processors/Port.h
index 0edc1123f38..9b2151e3469 100644
--- a/dbms/src/Processors/Port.h
+++ b/dbms/src/Processors/Port.h
@@ -16,9 +16,10 @@ class IProcessor;
 
 class Port
 {
-protected:
+    friend void connect(OutputPort &, InputPort &);
     friend class IProcessor;
 
+protected:
     /// Shared state of two connected ports.
     struct State
     {
diff --git a/dbms/src/Processors/QueueBuffer.h b/dbms/src/Processors/QueueBuffer.h
index 1593ae04118..da61f8d6f11 100644
--- a/dbms/src/Processors/QueueBuffer.h
+++ b/dbms/src/Processors/QueueBuffer.h
@@ -31,7 +31,7 @@ public:
 
         Block res = std::move(blocks.front());
         blocks.pop();
-        return std::move(res);
+        return res;
     }
 };