diff --git a/frameworks/qt5/qt5base/files/mkspecs/linux-openwrt-g++/qmake.conf b/frameworks/qt5/qt5base/files/mkspecs/linux-openwrt-g++/qmake.conf
index eff0868..c82f23b 100644
--- a/frameworks/qt5/qt5base/files/mkspecs/linux-openwrt-g++/qmake.conf
+++ b/frameworks/qt5/qt5base/files/mkspecs/linux-openwrt-g++/qmake.conf
@@ -10,6 +10,11 @@ include(../common/linux.conf)
 include(../common/gcc-base-unix.conf)
 include(../common/g++-unix.conf)
 
+QMAKE_CFLAGS_OPTIMIZE      =
+QMAKE_CFLAGS_OPTIMIZE_FULL =
+# for whatever reasons $QMAKE_C*FLAGS_RELEASE has set optimization flags directly, instead of referencing $QMAKE_CFLAGS_OPTIMIZE*, so clearing them explicitly, too
+QMAKE_CFLAGS_RELEASE   =
+QMAKE_CXXFLAGS_RELEASE = $$QMAKE_CFLAGS_RELEASE
 
 # modifications to gcc-base.conf (included by gcc-base-unix.conf)
 QMAKE_CFLAGS           += $$(TARGET_CFLAGS)