diff --git a/CMakeLists.txt b/CMakeLists.txt
index 56948dd2..e3708c50 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -156,9 +156,13 @@ if(X11_FOUND)
   find_path(XF86KEYSYM_H XF86keysym.h PATHS ${X11_INCLUDE_DIR})
   if(KEYSYMDEF_H)
     set(HAVE_KEYSYMDEF_H ON)
+  else()
+    message(WARNING, "Missing X11/keysymdef.h")
   endif()
   if(XF86KEYSYM_H)
     set(HAVE_XF86KEYSYM_H ON)
+  else()
+    message(WARNING, "Missing X11/XF86keysym.h")
   endif()
 endif(X11_FOUND)
 
diff --git a/src/globalshortcuts/keymapper_x11.h b/src/globalshortcuts/keymapper_x11.h
index d0e08dc3..1bffd319 100644
--- a/src/globalshortcuts/keymapper_x11.h
+++ b/src/globalshortcuts/keymapper_x11.h
@@ -28,9 +28,13 @@
 
 #ifdef HAVE_KEYSYMDEF_H
 #  include <X11/keysymdef.h>
+#else
+#  warning "Missing X11/keysymdef.h"
 #endif
 #ifdef HAVE_XF86KEYSYM_H
 #  include <X11/XF86keysym.h>
+#else
+#  warning "Missing X11/XF86keysym.h"
 #endif
 
 namespace KeyMapperX11 {