diff --git a/src/3rdparty/xkbcommon.pri b/src/3rdparty/xkbcommon.pri
index 99536576f71..d437c6b8b66 100644
--- a/src/3rdparty/xkbcommon.pri
+++ b/src/3rdparty/xkbcommon.pri
@@ -1,4 +1,4 @@
-QMAKE_CFLAGS = -std=gnu99 -w
+QMAKE_CFLAGS += -std=gnu99 -w
 INCLUDEPATH += $$PWD/xkbcommon $$PWD/xkbcommon/src $$PWD/xkbcommon/src/xkbcomp
 
 DEFINES += DFLT_XKB_CONFIG_ROOT='\\"/usr/share/X11/xkb\\"'