diff --git a/stix/configure b/stix/configure
index dc82f17..716a70f 100755
--- a/stix/configure
+++ b/stix/configure
@@ -18893,6 +18893,40 @@ cat >>confdefs.h <<_ACEOF
 _ACEOF
 
 
+# The cast to long int works around a bug in the HP C Compiler
+# version HP92453-01 B.11.11.23709.GP, which incorrectly rejects
+# declarations like `int a3[[(sizeof (unsigned char)) >= 0]];'.
+# This bug is HP SR number 8606223364.
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking size of __uint128_t" >&5
+$as_echo_n "checking size of __uint128_t... " >&6; }
+if ${ac_cv_sizeof___uint128_t+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  if ac_fn_c_compute_int "$LINENO" "(long int) (sizeof (__uint128_t))" "ac_cv_sizeof___uint128_t"        "
+"; then :
+
+else
+  if test "$ac_cv_type___uint128_t" = yes; then
+     { { $as_echo "$as_me:${as_lineno-$LINENO}: error: in \`$ac_pwd':" >&5
+$as_echo "$as_me: error: in \`$ac_pwd':" >&2;}
+as_fn_error 77 "cannot compute sizeof (__uint128_t)
+See \`config.log' for more details" "$LINENO" 5; }
+   else
+     ac_cv_sizeof___uint128_t=0
+   fi
+fi
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_sizeof___uint128_t" >&5
+$as_echo "$ac_cv_sizeof___uint128_t" >&6; }
+
+
+
+cat >>confdefs.h <<_ACEOF
+#define SIZEOF___UINT128_T $ac_cv_sizeof___uint128_t
+_ACEOF
+
+
 # The cast to long int works around a bug in the HP C Compiler
 # version HP92453-01 B.11.11.23709.GP, which incorrectly rejects
 # declarations like `int a3[[(sizeof (unsigned char)) >= 0]];'.
@@ -19257,6 +19291,7 @@ else
 			{ $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
 $as_echo "no" >&6; }
 			ac_cv_sizeof___int128_t=0
+			ac_cv_sizeof___uint128_t=0
 
 
 fi
@@ -19476,6 +19511,11 @@ cat >>confdefs.h <<_ACEOF
 _ACEOF
 
 
+cat >>confdefs.h <<_ACEOF
+#define STIX_SIZEOF___UINT128_T ${ac_cv_sizeof___uint128_t}
+_ACEOF
+
+
 cat >>confdefs.h <<_ACEOF
 #define STIX_SIZEOF_VOID_P ${ac_cv_sizeof_void_p}
 _ACEOF
diff --git a/stix/configure.ac b/stix/configure.ac
index bc8d3ae..e20ca92 100644
--- a/stix/configure.ac
+++ b/stix/configure.ac
@@ -210,6 +210,7 @@ AC_CHECK_SIZEOF(__int16_t,,[[]])
 AC_CHECK_SIZEOF(__int32_t,,[[]])
 AC_CHECK_SIZEOF(__int64_t,,[[]])
 AC_CHECK_SIZEOF(__int128_t,,[[]])
+AC_CHECK_SIZEOF(__uint128_t,,[[]])
 dnl AC_CHECK_SIZEOF doesn't work without white-space between void and *
 AC_CHECK_SIZEOF(void *,,[[]])
 AC_CHECK_SIZEOF(float,,[[]])
@@ -252,6 +253,7 @@ then
 		[
 			AC_MSG_RESULT(no)
 			ac_cv_sizeof___int128_t=0
+			ac_cv_sizeof___uint128_t=0
 		]
 	)
 fi
@@ -336,6 +338,7 @@ AC_DEFINE_UNQUOTED(STIX_SIZEOF___INT32, ${ac_cv_sizeof___int32}, [sizeof(__int32
 AC_DEFINE_UNQUOTED(STIX_SIZEOF___INT64, ${ac_cv_sizeof___int64}, [sizeof(__int64)])
 AC_DEFINE_UNQUOTED(STIX_SIZEOF___INT128, ${ac_cv_sizeof___int128}, [sizeof(__int128)])
 AC_DEFINE_UNQUOTED(STIX_SIZEOF___INT128_T, ${ac_cv_sizeof___int128_t}, [sizeof(__int128_t)])
+AC_DEFINE_UNQUOTED(STIX_SIZEOF___UINT128_T, ${ac_cv_sizeof___uint128_t}, [sizeof(__uint128_t)])
 AC_DEFINE_UNQUOTED(STIX_SIZEOF_VOID_P, ${ac_cv_sizeof_void_p}, [sizeof(void*)])
 AC_DEFINE_UNQUOTED(STIX_SIZEOF_FLOAT, ${ac_cv_sizeof_float}, [sizeof(float)])
 AC_DEFINE_UNQUOTED(STIX_SIZEOF_DOUBLE, ${ac_cv_sizeof_double}, [sizeof(double)])
diff --git a/stix/lib/stix-cfg.h.in b/stix/lib/stix-cfg.h.in
index a80eef0..a8067b7 100644
--- a/stix/lib/stix-cfg.h.in
+++ b/stix/lib/stix-cfg.h.in
@@ -414,6 +414,9 @@
 /* The size of `__int8_t', as computed by sizeof. */
 #undef SIZEOF___INT8_T
 
+/* The size of `__uint128_t', as computed by sizeof. */
+#undef SIZEOF___UINT128_T
+
 /* Define to 1 if you have the ANSI C header files. */
 #undef STDC_HEADERS
 
@@ -513,6 +516,9 @@
 /* sizeof(__int8) */
 #undef STIX_SIZEOF___INT8
 
+/* sizeof(__uint128_t) */
+#undef STIX_SIZEOF___UINT128_T
+
 /* Version number of package */
 #undef VERSION
 
diff --git a/stix/lib/stix-cmn.h b/stix/lib/stix-cmn.h
index 6588c30..db815c0 100644
--- a/stix/lib/stix-cmn.h
+++ b/stix/lib/stix-cmn.h
@@ -197,7 +197,10 @@
 #elif defined(STIX_SIZEOF___INT128_T) && (STIX_SIZEOF___INT128_T == 16)
 #	define STIX_HAVE_UINT128_T
 #	define STIX_HAVE_INT128_T
-	#if defined(__clang__)
+	#if defined(STIX_SIZEOF___UINT128_T) && (STIX_SIZEOF___UINT128_T == STIX_SIZEOF___INT128_T)
+	typedef __uint128_t  stix_uint128_t;
+	typedef __int128_t   stix_int128_t;
+	#elif defined(__clang__)
 	typedef __uint128_t  stix_uint128_t;
 	typedef __int128_t   stix_int128_t;
 	#else