diff --git a/include/boost/predef/hardware/simd/x86/sse4a.h b/include/boost/predef/hardware/simd/x86/sse4a.h
index 13c3710..348d229 100644
--- a/include/boost/predef/hardware/simd/x86/sse4a.h
+++ b/include/boost/predef/hardware/simd/x86/sse4a.h
@@ -9,4 +9,42 @@ http://www.boost.org/LICENSE_1_0.txt)
 #ifndef BOOST_PREDEF_HARDWARE_SIMD_X86_SSE4A_H
 #define BOOST_PREDEF_HARDWARE_SIMD_X86_SSE4A_H
 
+#include <boost/predef/version_number.h>
+
+/*`
+ [heading `BOOST_HW_SIMD_X86_SSE4A`]
+
+ [@https://en.wikipedia.org/wiki/SSE4##SSE4A SSE4A] x86 extension.
+ Version number is the default BOOST_VERSION_NUMBER_AVAILABLE.
+
+ This extension is only available on particular CPUs. It does imply
+ SSE3, but it is not implied by extensions newer than SSE3. For example,
+ SSE4.1 does not imply it.
+
+ [table
+     [[__predef_symbol__] [__predef_version__]]
+
+     [[`__SSE4A__`] [__predef_detection__]]
+     ]
+ */
+
+#define BOOST_HW_SIMD_X86_SSE4A BOOST_VERSION_NUMBER_NOT_AVAILABLE
+
+#if defined(__SSE4A__)
+#   undef BOOST_HW_SIMD_X86_SSE4A
+/* We do not give a valid version for this one, since it not always
+ * available if newer extension than SSE3 are enabled. */
+#   define BOOST_HW_SIMD_X86_SSE4A BOOST_VERSION_NUMBER_AVAILABLE
+#   define BOOST_HW_SIMD_X86_SSE4A_AVAILABLE
 #endif
+
+#define BOOST_HW_SIMD_X86_SSE4A_NAME "SSE4a"
+
+#if defined(BOOST_HW_SIMD_X86_SSE4A_AVAILABLE)
+#   include <ammintrin.h>
+#endif
+
+#endif
+
+#include <boost/predef/detail/test.h>
+BOOST_PREDEF_DECLARE_TEST(BOOST_HW_SIMD_X86_SSE4A, BOOST_HW_SIMD_X86_SSE4A_NAME)