diff --git a/src/gui/CMakeLists.txt b/src/gui/CMakeLists.txt
index e806bebba..8e7ca45de 100644
--- a/src/gui/CMakeLists.txt
+++ b/src/gui/CMakeLists.txt
@@ -181,6 +181,9 @@ if (APPLE)
         ../3rdparty/qtmacgoodies/src/macstandardicon.mm
         ../3rdparty/qtmacgoodies/src/macwindow.mm
         )
+    # We want to access Cocoa specific structures in the code above
+    # and need the platform plugin interface for that - which is private.
+    include_directories(${Qt5Gui_PRIVATE_INCLUDE_DIRS})
 endif()
 
 if(NOT WIN32)