diff --git a/repos/libports/lib/mk/mxtasking.mk b/repos/libports/lib/mk/mxtasking.mk
index f78b4f5d97..f02aae98c8 100644
--- a/repos/libports/lib/mk/mxtasking.mk
+++ b/repos/libports/lib/mk/mxtasking.mk
@@ -1,4 +1,5 @@
 MXTASKING_DIR := $(call select_from_ports,mxtasking)/src/lib/mxtasking
+GENODE_GCC_TOOLCHAIN_DIR := /usr/local/genode/tool/21.05
 
 SRC_CC = $(shell find $(MXTASKING_DIR)/src/mx -name '*.cpp')
 vpath %.cpp $(MXTASKING_DIR)/src/mx
@@ -6,14 +7,19 @@ vpath %.cpp $(MXTASKING_DIR)/src/mx
 INC_DIR += $(MXTASKING_DIR)/src $(MXTASKING_DIR)/lib
 vpath %.h ${INC_DIR}
 
-CC_OPT += -pedantic -Wall \
+CUSTOM_CXX = /usr/local/genode/tool/bin/clang++
+CUSTOM_CC = /usr/local/genode/tool/bin/clang
+
+CC_OPT += --target=x86_64-genode --sysroot=/does/not/exist --gcc-toolchain=$(GENODE_GCC_TOOLCHAIN_DIR) -DCLANG_CXX11_ATOMICS 
+CC_OPT += -std=c++17 -pedantic -Wall \
  -Wno-invalid-offsetof -Wcast-align -Wcast-qual -Wctor-dtor-privacy -Wdisabled-optimization \
  -Wformat=2 -Winit-self -Wmissing-declarations -Wmissing-include-dirs -Woverloaded-virtual \
  -Wredundant-decls -Wshadow -Wsign-promo -Wstrict-overflow=5 -Wswitch-default -Wundef \
- -Wno-unused -Wold-style-cast -Wno-uninitialized -O1 -g3 -fno-aligned-new
+ -Wno-unused -Wold-style-cast -Wno-uninitialized -O2 -g -DNDEBUG -fno-aligned-new
 
-CC_OPT += $(addprefix -I ,$(INC_DIR))
+CC_OPT += $(addprefix -I ,$(INC_DIR)) 
 CC_CXX_WARN_STRICT =
 
 LIBS += base libm libc stdcxx
+EXT_OBJECTS += /usr/local/genode/tool/lib/clang/14.0.5/lib/linux/libclang_rt.builtins-x86_64.a /usr/local/genode/tool/lib/libatomic.a 
 #SHARED_LIB = yes