diff --git a/src/liblzma/common/memcmplen.h b/src/liblzma/common/memcmplen.h
index 99d9c519..81922ba2 100644
--- a/src/liblzma/common/memcmplen.h
+++ b/src/liblzma/common/memcmplen.h
@@ -57,7 +57,8 @@ lzma_memcmplen(const uint8_t *buf1, const uint8_t *buf2,
 	assert(limit <= UINT32_MAX / 2);
 
 #if defined(TUKLIB_FAST_UNALIGNED_ACCESS) \
-		&& ((TUKLIB_GNUC_REQ(3, 4) && defined(__x86_64__)) \
+		&& (((TUKLIB_GNUC_REQ(3, 4) || defined(__clang__)) \
+				&& defined(__x86_64__)) \
 			|| (defined(__INTEL_COMPILER) && defined(__x86_64__)) \
 			|| (defined(__INTEL_COMPILER) && defined(_M_X64)) \
 			|| (defined(_MSC_VER) && defined(_M_X64)))