diff --git a/config.h b/config.h
index 0a10fecc..e7b1bb36 100644
--- a/config.h
+++ b/config.h
@@ -354,13 +354,14 @@ NAMESPACE_END
 
 // Sun Studio Express 3 (December 2006) provides GCC-style attributes.
 // IBM XL C/C++ alignment modifier per Optimization Guide, pp. 19-20.
+// __IBM_ATTRIBUTES per XLC 12.1 AIX Compiler Manual, p. 473.
 // CRYPTOPP_ALIGN_DATA may not be reliable on AIX.
 #ifndef CRYPTOPP_ALIGN_DATA
 	#if defined(_MSC_VER)
 		#define CRYPTOPP_ALIGN_DATA(x) __declspec(align(x))
 	#elif defined(__GNUC__) || (__SUNPRO_CC >= 0x5100)
 		#define CRYPTOPP_ALIGN_DATA(x) __attribute__((aligned(x)))
-	#elif defined(__xlc__) || defined(__xlC__)
+	#elif defined(__xlc__) || defined(__xlC__) || defined(__IBM_ATTRIBUTES)
 		#define CRYPTOPP_ALIGN_DATA(x) __attribute__((aligned(x)))
 	#else
 		#define CRYPTOPP_ALIGN_DATA(x)
diff --git a/misc.h b/misc.h
index 086f76ed..0e420f9a 100644
--- a/misc.h
+++ b/misc.h
@@ -1060,6 +1060,8 @@ inline unsigned int GetAlignmentOf()
 	return __alignof__(T);
 #elif defined(__SUNPRO_CC)
 	return __alignof__(T);
+#elif defined(__IBM_ALIGNOF__)
+	return __alignof__(T);
 #elif CRYPTOPP_BOOL_SLOW_WORD64
 	return UnsignedMin(4U, sizeof(T));
 #else