diff --git a/src/openrct2-ui/CMakeLists.txt b/src/openrct2-ui/CMakeLists.txt
index d6f5cff0ff..d009c4122d 100644
--- a/src/openrct2-ui/CMakeLists.txt
+++ b/src/openrct2-ui/CMakeLists.txt
@@ -35,7 +35,8 @@ endif ()
 
 # Sources
 file(GLOB_RECURSE OPENRCT2_UI_SOURCES
-    "${CMAKE_CURRENT_LIST_DIR}/*.cpp"
+    "${CMAKE_CURRENT_LIST_DIR}/*.cpp")
+file(GLOB_RECURSE OPENRCT2_UI_HEADERS
     "${CMAKE_CURRENT_LIST_DIR}/*.h"
     "${CMAKE_CURRENT_LIST_DIR}/*.hpp")
 
@@ -97,3 +98,19 @@ endif ()
 if (MSVC)
     add_definitions(-D__DISABLE_DLL_PROXY__)
 endif ()
+
+# Add headers check to verify all headers carry their dependencies.
+# Only valid for Clang for now:
+# - GCC 8 does not support -Wno-pragma-once-outside-header
+# - Other compilers status unknown
+if ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang")
+    set(OPENRCT2_HEADERS_CHECK ${OPENRCT2_UI_HEADERS})
+    # OpenGLAPIProc.h is not meant to be included directly.
+    list(REMOVE_ITEM OPENRCT2_HEADERS_CHECK "${CMAKE_CURRENT_LIST_DIR}/drawing/engines/opengl/OpenGLAPIProc.h")
+    add_library(${PROJECT}-headers-check OBJECT ${OPENRCT2_HEADERS_CHECK})
+    set_target_properties(${PROJECT}-headers-check PROPERTIES LINKER_LANGUAGE CXX)
+    set_source_files_properties(${OPENRCT2_HEADERS_CHECK} PROPERTIES LANGUAGE CXX)
+    add_definitions("-x c++ -Wno-pragma-once-outside-header -Wno-unused-const-variable")
+    get_target_property(OPENRCT2_INCLUDE_DIRS ${PROJECT} INCLUDE_DIRECTORIES)
+    set_target_properties(${PROJECT}-headers-check PROPERTIES INCLUDE_DIRECTORIES ${OPENRCT2_INCLUDE_DIRS})
+endif ()
diff --git a/src/openrct2/CMakeLists.txt b/src/openrct2/CMakeLists.txt
index 1d59906fa2..61811ce0fc 100644
--- a/src/openrct2/CMakeLists.txt
+++ b/src/openrct2/CMakeLists.txt
@@ -59,8 +59,8 @@ if (NOT DISABLE_TTF)
 endif ()
 
 # Sources
-file(GLOB_RECURSE OPENRCT2_CORE_SOURCES "${CMAKE_CURRENT_LIST_DIR}/*.cpp"
-                                        "${CMAKE_CURRENT_LIST_DIR}/*.h"
+file(GLOB_RECURSE OPENRCT2_CORE_SOURCES "${CMAKE_CURRENT_LIST_DIR}/*.cpp")
+file(GLOB_RECURSE OPENRCT2_CORE_HEADERS "${CMAKE_CURRENT_LIST_DIR}/*.h"
                                         "${CMAKE_CURRENT_LIST_DIR}/*.hpp")
 if (APPLE)
     file(GLOB_RECURSE OPENRCT2_CORE_MM_SOURCES "${CMAKE_CURRENT_LIST_DIR}/*.mm")
@@ -179,3 +179,19 @@ if((X86 OR X86_64) AND NOT MSVC)
     set_source_files_properties(${CMAKE_CURRENT_LIST_DIR}/drawing/SSE41Drawing.cpp PROPERTIES COMPILE_FLAGS -msse4.1)
     set_source_files_properties(${CMAKE_CURRENT_LIST_DIR}/drawing/AVX2Drawing.cpp PROPERTIES COMPILE_FLAGS -mavx2)
 endif()
+
+# Add headers check to verify all headers carry their dependencies.
+# Only valid for Clang for now:
+# - GCC 8 does not support -Wno-pragma-once-outside-header
+# - Other compilers status unknown
+if ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang")
+    add_library(${PROJECT}-headers-check OBJECT ${OPENRCT2_CORE_HEADERS})
+    set_target_properties(${PROJECT}-headers-check PROPERTIES LINKER_LANGUAGE CXX)
+    set_source_files_properties(${OPENRCT2_CORE_HEADERS} PROPERTIES LANGUAGE CXX)
+    add_definitions("-x c++ -Wno-pragma-once-outside-header -Wno-unused-const-variable")
+    get_target_property(LIBOPENRCT2_INCLUDE_DIRS ${PROJECT} INCLUDE_DIRECTORIES)
+    set_target_properties(${PROJECT}-headers-check PROPERTIES INCLUDE_DIRECTORIES ${LIBOPENRCT2_INCLUDE_DIRS})
+else ()
+    # Dummy target to ease invocation
+    add_custom_target(${PROJECT}-headers-check)
+endif ()
diff --git a/src/openrct2/localisation/Localisation.h b/src/openrct2/localisation/Localisation.h
index 7ec140d222..70eb7adb48 100644
--- a/src/openrct2/localisation/Localisation.h
+++ b/src/openrct2/localisation/Localisation.h
@@ -84,7 +84,7 @@ extern const rct_string_id DateDayNames[31];
 extern const rct_string_id DateGameMonthNames[MONTH_COUNT];
 extern const rct_string_id DateGameShortMonthNames[MONTH_COUNT];
 
-static inline void set_format_arg_body(uint8 *args, size_t offset, uintptr_t value, size_t size)
+[[maybe_unused]] static inline void set_format_arg_body(uint8 *args, size_t offset, uintptr_t value, size_t size)
 {
     memcpy(args + offset, &value, size);
 }