diff --git a/libcxx/include/__format/parser_std_format_spec.h b/libcxx/include/__format/parser_std_format_spec.h
--- a/libcxx/include/__format/parser_std_format_spec.h
+++ b/libcxx/include/__format/parser_std_format_spec.h
@@ -1271,7 +1271,7 @@
   size_t __result = 0;
 
   while (__first != __last) {
-    wchar_t __c = *__first;
+    uint32_t __c = *__first;
     __result += __column_width(__c);
 
     if (__result > __maximum)
diff --git a/libcxx/test/libcxx/utilities/format/format.string/format.string.std/std_format_spec_string_unicode.pass.cpp b/libcxx/test/libcxx/utilities/format/format.string/format.string.std/std_format_spec_string_unicode.pass.cpp
--- a/libcxx/test/libcxx/utilities/format/format.string/format.string.std/std_format_spec_string_unicode.pass.cpp
+++ b/libcxx/test/libcxx/utilities/format/format.string/format.string.std/std_format_spec_string_unicode.pass.cpp
@@ -9,9 +9,6 @@
 // UNSUPPORTED: libcpp-no-concepts
 // UNSUPPORTED: libcpp-has-no-incomplete-format
 
-// Fails for 32-bit builds on AIX.
-// UNSUPPORTED: LIBCXX-AIX-FIXME
-
 // UTF-32 doesn't work properly
 // XFAIL: windows