diff --git a/src/AsyncEventSource.h b/src/AsyncEventSource.h
index 6754694..a000de2 100644
--- a/src/AsyncEventSource.h
+++ b/src/AsyncEventSource.h
@@ -82,7 +82,7 @@ class AsyncEventSourceResponse: public AsyncWebServerResponse {
     AsyncEventSourceResponse(AsyncEventSource *server);
     void _respond(AsyncWebServerRequest *request);
     size_t _ack(AsyncWebServerRequest *request, size_t len, uint32_t time);
-    bool _sourceValid(){ return true; }
+    bool _sourceValid() const { return true; }
 };
 
 
diff --git a/src/AsyncJson.h b/src/AsyncJson.h
index a1d3772..966a659 100644
--- a/src/AsyncJson.h
+++ b/src/AsyncJson.h
@@ -65,7 +65,7 @@ class AsyncJsonResponse: public AsyncAbstractResponse {
     }
     ~AsyncJsonResponse() {}
     JsonVariant & getRoot() { return _root; }
-    bool _sourceValid() { return _isValid; }
+    bool _sourceValid() const { return _isValid; }
     size_t setLength() {
       _contentLength = _root.measureLength();
       if (_contentLength) { _isValid = true; }
diff --git a/src/AsyncWebSocket.cpp b/src/AsyncWebSocket.cpp
index 56c7bb2..b0c1a78 100644
--- a/src/AsyncWebSocket.cpp
+++ b/src/AsyncWebSocket.cpp
@@ -154,7 +154,7 @@ class AsyncWebSocketControl {
       if(_data != NULL)
         free(_data);
     }
-    virtual bool finished(){ return _finished; }
+    virtual bool finished() const { return _finished; }
     uint8_t opcode(){ return _opcode; }
     uint8_t len(){ return _len + 2; }
     size_t send(AsyncClient *client){
diff --git a/src/AsyncWebSocket.h b/src/AsyncWebSocket.h
index 1ef7d7b..87a5f53 100644
--- a/src/AsyncWebSocket.h
+++ b/src/AsyncWebSocket.h
@@ -219,7 +219,7 @@ class AsyncWebSocketResponse: public AsyncWebServerResponse {
     AsyncWebSocketResponse(const String& key, AsyncWebSocket *server);
     void _respond(AsyncWebServerRequest *request);
     size_t _ack(AsyncWebServerRequest *request, size_t len, uint32_t time);
-    bool _sourceValid(){ return true; }
+    bool _sourceValid() const { return true; }
 };