diff --git a/Make.defaults b/Make.defaults
index 51bd7d8..16f1fd2 100755
--- a/Make.defaults
+++ b/Make.defaults
@@ -101,6 +101,7 @@ endif
 ifeq ($(ARCH),x86_64)
   GCCVERSION   := $(shell $(CC) -dumpversion | cut -f1 -d.)
   GCCMINOR     := $(shell $(CC) -dumpversion | cut -f2 -d.)
+  USING_CLANG  := $(shell $(CC) -v 2>&1 | grep -q 'clang version' && echo clang)
 
   # Rely on GCC MS ABI support?
   GCCNEWENOUGH := $(shell ( [ $(GCCVERSION) -gt "4" ]           \
@@ -109,6 +110,8 @@ ifeq ($(ARCH),x86_64)
                           && echo 1)
   ifeq ($(GCCNEWENOUGH),1)
     CPPFLAGS += -DGNU_EFI_USE_MS_ABI -maccumulate-outgoing-args --std=c11
+  else ifeq ($(USING_CLANG),clang)
+    CPPFLAGS += -DGNU_EFI_USE_MS_ABI --std=c11
   endif
 
   CFLAGS += -mno-red-zone
@@ -159,7 +162,7 @@ CFLAGS  += $(ARCH3264) -g -O2 -Wall -Wextra -Werror \
 else
 CFLAGS  += $(ARCH3264) -g -O2 -Wall -Wextra -Werror \
            -fshort-wchar -fno-strict-aliasing \
-           -fno-merge-constants -ffreestanding -fno-stack-protector \
+           -fno-merge-all-constants -ffreestanding -fno-stack-protector \
            -fno-stack-check
 endif
 
diff --git a/apps/debughook.c b/apps/debughook.c
index fb6cdad..93cd0cf 100644
--- a/apps/debughook.c
+++ b/apps/debughook.c
@@ -37,8 +37,13 @@ GetVariable(CHAR16 *var, UINT8 **data, UINTN *len, EFI_GUID owner)
 EFI_GUID DUMMY_GUID =
 {0x55aad538, 0x8f82, 0x4e2a, {0xa4,0xf0,0xbe, 0x59, 0x13, 0xb6, 0x5f, 0x1e}};
 
-static void
-__attribute__((__optimize__("0")))
+#if defined(__clang__)
+# define _OPTNONE __attribute__((optnone))
+#else
+# define _OPTNONE __attribute__((__optimize__("0")))
+#endif
+
+static _OPTNONE void
 DebugHook(void)
 {
 	EFI_GUID guid = DUMMY_GUID;
diff --git a/inc/x86_64/efibind.h b/inc/x86_64/efibind.h
index 5ee620b..de37641 100644
--- a/inc/x86_64/efibind.h
+++ b/inc/x86_64/efibind.h
@@ -25,6 +25,8 @@ Revision History
 #if defined(GNU_EFI_USE_MS_ABI)
     #if defined(__GNUC__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 7))
         #define HAVE_USE_MS_ABI 1
+    #elif defined(__clang__)
+        #define HAVE_USE_MS_ABI 1
     #else
         #error Compiler is too old for GNU_EFI_USE_MS_ABI
     #endif
diff --git a/lib/guid.c b/lib/guid.c
index bd1f1a5..8daa505 100644
--- a/lib/guid.c
+++ b/lib/guid.c
@@ -97,7 +97,7 @@ static struct {
 	{  &SMapId,                                         L"ShellDevPathMap" },
 	{  &SAliasId,                                       L"ShellAlias" },
 
-	{  NULL }
+	{  NULL, NULL }
 };
 
 //