diff --git a/src/openrct2/actions/PlaceParkEntranceAction.cpp b/src/openrct2/actions/PlaceParkEntranceAction.cpp
index 0ebd1403a0..e0ec265bab 100644
--- a/src/openrct2/actions/PlaceParkEntranceAction.cpp
+++ b/src/openrct2/actions/PlaceParkEntranceAction.cpp
@@ -216,7 +216,7 @@ public:
 	}
 };
 
-static auto Factory = GameActions::Register<PlaceParkEntranceAction>(GAME_COMMAND_PLACE_PARK_ENTRANCE);
+static auto Factory UNUSED_ATTR = GameActions::Register<PlaceParkEntranceAction>(GAME_COMMAND_PLACE_PARK_ENTRANCE);
 
 extern "C"
 {
diff --git a/src/openrct2/actions/SetParkEntranceFeeAction.cpp b/src/openrct2/actions/SetParkEntranceFeeAction.cpp
index df45b3bc16..1a9b2fb06c 100644
--- a/src/openrct2/actions/SetParkEntranceFeeAction.cpp
+++ b/src/openrct2/actions/SetParkEntranceFeeAction.cpp
@@ -73,7 +73,7 @@ public:
     }
 };
 
-static auto Factory = GameActions::Register<SetParkEntranceFeeAction>(GAME_COMMAND_SET_PARK_ENTRANCE_FEE);
+static auto Factory UNUSED_ATTR = GameActions::Register<SetParkEntranceFeeAction>(GAME_COMMAND_SET_PARK_ENTRANCE_FEE);
 
 extern "C"
 {
diff --git a/src/openrct2/common.h b/src/openrct2/common.h
index c23ee0b6a0..3314c05fa9 100644
--- a/src/openrct2/common.h
+++ b/src/openrct2/common.h
@@ -247,6 +247,17 @@ typedef uint16 rct_string_id;
     #define FASTCALL
 #endif // PLATFORM_X86
 
+// C++17 or later
+#if defined(__cplusplus) && __cplusplus > 201402L
+	#define UNUSED_ATTR [[maybe_unused]]
+#else
+	#ifdef __GNUC__
+		#define UNUSED_ATTR [[gnu::unused]]
+	#else
+		#define UNUSED_ATTR
+	#endif
+#endif
+
 /**
  * x86 register structure, only used for easy interop to RCT2 code.
  */