diff --git a/hecl-gui/CMakeLists.txt b/hecl-gui/CMakeLists.txt
index fa30cdd59..d790559b6 100644
--- a/hecl-gui/CMakeLists.txt
+++ b/hecl-gui/CMakeLists.txt
@@ -23,7 +23,7 @@ endif()
 
 add_subdirectory(platforms/freedesktop)
 declare_qticon_target()
-list(APPEND PLAT_SRCS mainicon_qt.c)
+list(APPEND PLAT_SRCS mainicon_qt.cpp)
 
 add_executable(hecl-gui WIN32 MACOSX_BUNDLE
     MainWindow.ui MainWindow.hpp MainWindow.cpp
diff --git a/hecl-gui/platforms/freedesktop/CMakeLists.txt b/hecl-gui/platforms/freedesktop/CMakeLists.txt
index a9fbfc84d..00866479f 100644
--- a/hecl-gui/platforms/freedesktop/CMakeLists.txt
+++ b/hecl-gui/platforms/freedesktop/CMakeLists.txt
@@ -14,5 +14,5 @@ add_custom_command(OUTPUT ${CMAKE_BINARY_DIR}/hecl-gui/platforms/freedesktop/mai
                    ${CMAKE_SOURCE_DIR}/hecl-gui/platforms/freedesktop/16x16/apps/hecl.png
                    WORKING_DIRECTORY ${CMAKE_SOURCE_DIR}/hecl-gui/platforms/freedesktop
                    COMMENT "Generating mainicon_qt.bin")
-bintoc(mainicon_qt.c ${CMAKE_BINARY_DIR}/hecl-gui/platforms/freedesktop/mainicon_qt.bin MAINICON_QT)
+bintoc(mainicon_qt.cpp ${CMAKE_BINARY_DIR}/hecl-gui/platforms/freedesktop/mainicon_qt.bin MAINICON_QT)
 endmacro()