diff --git a/libcxx/include/__locale b/libcxx/include/__locale
--- a/libcxx/include/__locale
+++ b/libcxx/include/__locale
@@ -492,7 +492,11 @@
     static const mask punct  = _ISPUNCT;
     static const mask xdigit = _ISXDIGIT;
     static const mask blank  = _ISBLANK;
+# if defined(_AIX)
+    static const mask __regex_word = 0x8000;
+# else
     static const mask __regex_word = 0x80;
+# endif
 #elif defined(_NEWLIB_VERSION)
     // Same type as Newlib's _ctype_ array in newlib/libc/include/ctype.h.
     typedef char mask;
@@ -545,11 +549,8 @@
 
     _LIBCPP_INLINE_VISIBILITY ctype_base() {}
 
-// TODO: Remove the ifndef when the assert no longer fails on AIX.
-#ifndef _AIX
     static_assert((__regex_word & ~(space | print | cntrl | upper | lower | alpha | digit | punct | xdigit | blank)) == __regex_word,
                   "__regex_word can't overlap other bits");
-#endif
 };
 
 template <class _CharT> class _LIBCPP_TEMPLATE_VIS ctype;
diff --git a/libcxx/test/std/re/re.traits/isctype.pass.cpp b/libcxx/test/std/re/re.traits/isctype.pass.cpp
--- a/libcxx/test/std/re/re.traits/isctype.pass.cpp
+++ b/libcxx/test/std/re/re.traits/isctype.pass.cpp
@@ -6,8 +6,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-// XFAIL: LIBCXX-AIX-FIXME
-
 // <regex>
 
 // template <class charT> struct regex_traits;
diff --git a/libcxx/test/std/re/re.traits/lookup_classname.pass.cpp b/libcxx/test/std/re/re.traits/lookup_classname.pass.cpp
--- a/libcxx/test/std/re/re.traits/lookup_classname.pass.cpp
+++ b/libcxx/test/std/re/re.traits/lookup_classname.pass.cpp
@@ -6,8 +6,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-// XFAIL: LIBCXX-AIX-FIXME
-
 // <regex>
 
 // template <class charT> struct regex_traits;