diff --git a/tools/fuzz/x86_instruction_emulator/Makefile b/tools/fuzz/x86_instruction_emulator/Makefile
index a97f50781e..505de39ab0 100644
--- a/tools/fuzz/x86_instruction_emulator/Makefile
+++ b/tools/fuzz/x86_instruction_emulator/Makefile
@@ -14,7 +14,7 @@ x86_emulate/x86_emulate.c x86_emulate/x86_emulate.h:
 x86_emulate.c x86_emulate.h: %:
 	[ -L $* ] || ln -sf $(XEN_ROOT)/tools/tests/x86_emulator/$*
 
-CFLAGS += $(CFLAGS_xeninclude)
+CFLAGS += $(CFLAGS_xeninclude) -D__XEN_TOOLS__
 
 x86_emulate.o: x86_emulate.c x86_emulate.h x86_emulate/x86_emulate.c x86_emulate/x86_emulate.h