diff --git a/Source/controls/devices/game_controller.cpp b/Source/controls/devices/game_controller.cpp
index 0cbdf34ef..dc728190d 100644
--- a/Source/controls/devices/game_controller.cpp
+++ b/Source/controls/devices/game_controller.cpp
@@ -81,7 +81,7 @@ ControllerButton GameController::ToControllerButton(const SDL_Event &event)
 	return ControllerButton_NONE;
 }
 
-SDL_GameControllerButton GameController::ToSdlGameControllerButton(ControllerButton button) const
+SDL_GameControllerButton GameController::ToSdlGameControllerButton(ControllerButton button)
 {
 	if (button == ControllerButton_AXIS_TRIGGERLEFT || button == ControllerButton_AXIS_TRIGGERRIGHT)
 		UNIMPLEMENTED();
diff --git a/Source/controls/devices/game_controller.h b/Source/controls/devices/game_controller.h
index 1d60a542f..17340fc8e 100644
--- a/Source/controls/devices/game_controller.h
+++ b/Source/controls/devices/game_controller.h
@@ -26,10 +26,10 @@ public:
 	ControllerButton ToControllerButton(const SDL_Event &event);
 
 	bool IsPressed(ControllerButton button) const;
-	bool ProcessAxisMotion(const SDL_Event &event);
+	static bool ProcessAxisMotion(const SDL_Event &event);
 
 private:
-	SDL_GameControllerButton ToSdlGameControllerButton(ControllerButton button) const;
+	static SDL_GameControllerButton ToSdlGameControllerButton(ControllerButton button);
 
 	SDL_GameController *sdl_game_controller_ = NULL;
 	SDL_JoystickID instance_id_ = -1;
diff --git a/Source/controls/devices/joystick.cpp b/Source/controls/devices/joystick.cpp
index e46918c59..e2014480a 100644
--- a/Source/controls/devices/joystick.cpp
+++ b/Source/controls/devices/joystick.cpp
@@ -12,7 +12,7 @@ extern bool sgbControllerActive;
 
 std::vector<Joystick> *const Joystick::joysticks_ = new std::vector<Joystick>;
 
-ControllerButton Joystick::ToControllerButton(const SDL_Event &event) const
+ControllerButton Joystick::ToControllerButton(const SDL_Event &event)
 {
 	switch (event.type) {
 	case SDL_JOYBUTTONDOWN:
@@ -111,7 +111,7 @@ ControllerButton Joystick::ToControllerButton(const SDL_Event &event) const
 	return ControllerButton_NONE;
 }
 
-int Joystick::ToSdlJoyButton(ControllerButton button) const
+int Joystick::ToSdlJoyButton(ControllerButton button)
 {
 	if (button == ControllerButton_AXIS_TRIGGERLEFT || button == ControllerButton_AXIS_TRIGGERRIGHT)
 		UNIMPLEMENTED();
@@ -177,7 +177,7 @@ int Joystick::ToSdlJoyButton(ControllerButton button) const
 	}
 }
 
-bool Joystick::IsHatButtonPressed(ControllerButton button) const
+bool Joystick::IsHatButtonPressed(ControllerButton button)
 {
 	switch (button) {
 #if defined(JOY_HAT_DPAD_UP_HAT) && defined(JOY_HAT_DPAD_UP)
diff --git a/Source/controls/devices/joystick.h b/Source/controls/devices/joystick.h
index cb6ff8471..d3d6295c2 100644
--- a/Source/controls/devices/joystick.h
+++ b/Source/controls/devices/joystick.h
@@ -25,9 +25,9 @@ public:
 	static const std::vector<Joystick> &All();
 	static bool IsPressedOnAnyJoystick(ControllerButton button);
 
-	ControllerButton ToControllerButton(const SDL_Event &event) const;
+	static ControllerButton ToControllerButton(const SDL_Event &event);
 	bool IsPressed(ControllerButton button) const;
-	bool ProcessAxisMotion(const SDL_Event &event);
+	static bool ProcessAxisMotion(const SDL_Event &event);
 
 	SDL_JoystickID instance_id() const
 	{
@@ -35,8 +35,8 @@ public:
 	}
 
 private:
-	int ToSdlJoyButton(ControllerButton button) const;
-	bool IsHatButtonPressed(ControllerButton button) const;
+	static int ToSdlJoyButton(ControllerButton button);
+	static bool IsHatButtonPressed(ControllerButton button);
 
 	SDL_Joystick *sdl_joystick_ = NULL;
 	SDL_JoystickID instance_id_ = -1;
diff --git a/Source/dvlnet/protocol_zt.h b/Source/dvlnet/protocol_zt.h
index dc4ee9c84..a848cea87 100644
--- a/Source/dvlnet/protocol_zt.h
+++ b/Source/dvlnet/protocol_zt.h
@@ -62,7 +62,7 @@ public:
 	bool send_oob_mc(const buffer_t &data);
 	bool recv(endpoint &peer, buffer_t &data);
 	bool network_online();
-	std::string make_default_gamename();
+	static std::string make_default_gamename();
 
 private:
 	static constexpr uint32_t PKTBUF_LEN = 65536;
@@ -80,12 +80,12 @@ private:
 	int fd_tcp = -1;
 	int fd_udp = -1;
 
-	uint64_t current_ms();
+	static uint64_t current_ms();
 	void close_all();
 
-	void set_nonblock(int fd);
-	void set_nodelay(int fd);
-	void set_reuseaddr(int fd);
+	static void set_nonblock(int fd);
+	static void set_nodelay(int fd);
+	static void set_reuseaddr(int fd);
 
 	bool send_queued_peer(const endpoint &peer);
 	bool recv_peer(const endpoint &peer);