diff --git a/Config.mk b/Config.mk
index 0fa4591379..4735a1bfd0 100644
--- a/Config.mk
+++ b/Config.mk
@@ -6,6 +6,8 @@ endif
 
 # Convenient variables
 comma   := ,
+open    := (
+close   := )
 squote  := '
 #' Balancing squote, to help syntax highlighting
 empty   :=
diff --git a/xen/arch/x86/Rules.mk b/xen/arch/x86/Rules.mk
index 659ac3d83e..0794afa3c3 100644
--- a/xen/arch/x86/Rules.mk
+++ b/xen/arch/x86/Rules.mk
@@ -81,6 +81,6 @@ $(call as-option-add,CFLAGS,CC,".include \"asm/indirect_thunk_asm.h\"",,\
 # Check whether clang keeps .macro-s between asm()-s:
 # https://bugs.llvm.org/show_bug.cgi?id=36110
 $(call as-option-add,CFLAGS,CC,\
-                     ".macro FOO\n.endm\"); asm volatile (\".macro FOO\n.endm",\
+                     ".macro FOO;.endm"$$(close); asm volatile $$(open)".macro FOO;.endm",\
                      -no-integrated-as)
 endif