diff --git a/Makefile b/Makefile
index 2880d3fd4..616c861ee 100644
--- a/Makefile
+++ b/Makefile
@@ -92,8 +92,8 @@ CLANG_VERSION = $(shell $(CMD_CLANG) --version 2>/dev/null | \
 	| .check_$(CMD_CLANG)
 #
 	@echo $(shell date)
-	@if [ ${CLANG_VERSION} -lt 12 ]; then
-		echo -n "you MUST use clang 12 or newer, "
+	@if [ ${CLANG_VERSION} -lt 9 ]; then
+		echo -n "you MUST use clang 9 or newer, "
 		echo "your current clang version is ${CLANG_VERSION}"
 		exit 1
 	fi
diff --git a/README.md b/README.md
index b2d2472a3..1e4e32a16 100644
--- a/README.md
+++ b/README.md
@@ -166,9 +166,9 @@ Linux Kernel: >= 4.15.
 
 ## Tools 
 * golang 1.17
-* clang 12.0.0
+* clang 9.0
 * cmake 3.18.4
-* clang backend: llvm 12.0.0
+* clang backend: llvm 9.0
 * kernel config:CONFIG_DEBUG_INFO_BTF=y (Optional, 2022-04-17)
 
 ## command
diff --git a/README_CN.md b/README_CN.md
index 6c5f26bab..9474624e6 100644
--- a/README_CN.md
+++ b/README_CN.md
@@ -181,9 +181,9 @@ hook了`/bin/bash`的`readline`函数。
 
 ## 工具链版本
 * golang 1.17
-* clang 12.0.0
+* clang 9.0
 * cmake 3.18.4
-* clang backend: llvm 12.0.0
+* clang backend: llvm 9.0
 * kernel config:CONFIG_DEBUG_INFO_BTF=y (可选，2022-04-17增加)
 
 
diff --git a/kern/ecapture.h b/kern/ecapture.h
index 6cd2f0fcb..16eb06920 100644
--- a/kern/ecapture.h
+++ b/kern/ecapture.h
@@ -12,6 +12,24 @@
 #else
 //CO:RE is disabled
 #include <linux/kconfig.h>
+
+// see https://github.com/ehids/ecapture/issues/256 for more detail.
+/*
+* This will bring in asm_volatile_goto and asm_inline macro definitions
+* if enabled by compiler and config options.
+*/
+#include <linux/types.h>
+
+/*
+* asm_inline is defined as asm __inline in "include/linux/compiler_types.h"
+* if supported by the kernel's CC (i.e CONFIG_CC_HAS_ASM_INLINE) which is not
+* supported by CLANG.
+*/
+#ifdef asm_inline
+#undef asm_inline
+#define asm_inline asm
+#endif
+
 #include <uapi/linux/ptrace.h>
 #include <linux/bpf.h>
 #include <linux/socket.h>