diff --git a/mesosphere/kernel/Makefile b/mesosphere/kernel/Makefile
index 8e52868b6..4c1317b1e 100644
--- a/mesosphere/kernel/Makefile
+++ b/mesosphere/kernel/Makefile
@@ -87,6 +87,8 @@ $(OUTPUT).elf	:	$(OFILES) ../../../libraries/libmesosphere/lib/libmesosphere.a
 
 $(OFILES_SRC)	: $(HFILES_BIN)
 
+kern_libc_generic.o: CFLAGS += -fno-builtin
+
 #---------------------------------------------------------------------------------
 # you need a rule like this for each extension you use as binary data
 #---------------------------------------------------------------------------------
diff --git a/mesosphere/kernel_ldr/Makefile b/mesosphere/kernel_ldr/Makefile
index 8e52868b6..4c1317b1e 100644
--- a/mesosphere/kernel_ldr/Makefile
+++ b/mesosphere/kernel_ldr/Makefile
@@ -87,6 +87,8 @@ $(OUTPUT).elf	:	$(OFILES) ../../../libraries/libmesosphere/lib/libmesosphere.a
 
 $(OFILES_SRC)	: $(HFILES_BIN)
 
+kern_libc_generic.o: CFLAGS += -fno-builtin
+
 #---------------------------------------------------------------------------------
 # you need a rule like this for each extension you use as binary data
 #---------------------------------------------------------------------------------