Index: subversion/include/svn_utf.h
===================================================================
--- subversion/include/svn_utf.h	(revision 18468)
+++ subversion/include/svn_utf.h	(working copy)
@@ -34,6 +34,16 @@
 #endif /* __cplusplus */
 
 
+#ifndef AS400
+#define SVN_APR_LOCALE_CHARSET APR_LOCALE_CHARSET
+#define SVN_APR_DEFAULT_CHARSET APR_DEFAULT_CHARSET
+#else
+/* APR_LOCALE_CHARSET and APR_DEFAULT_CHARSET are defined as ints on
+ * OS400. */
+#define SVN_APR_LOCALE_CHARSET (const char*)APR_LOCALE_CHARSET
+#define SVN_APR_DEFAULT_CHARSET (const char*)APR_DEFAULT_CHARSET
+#endif
+
 /**
  * Initialize the UTF-8 encoding/decoding routines.
  * Allocate cached translation handles in a subpool of @a pool.
Index: subversion/libsvn_client/diff.c
===================================================================
--- subversion/libsvn_client/diff.c	(revision 18468)
+++ subversion/libsvn_client/diff.c	(working copy)
@@ -2548,7 +2548,7 @@
 {
   return svn_client_diff3 (options, path1, revision1, path2, revision2,
                            recurse, ignore_ancestry, no_diff_deleted,
-                           ignore_content_type, APR_LOCALE_CHARSET,
+                           ignore_content_type, SVN_APR_LOCALE_CHARSET,
                            outfile, errfile, ctx, pool);
 }
 
@@ -2648,7 +2648,7 @@
   return svn_client_diff_peg3 (options, path, peg_revision, start_revision,
                                end_revision, recurse, ignore_ancestry,
                                no_diff_deleted, ignore_content_type,
-                               APR_LOCALE_CHARSET, outfile, errfile,
+                               SVN_APR_LOCALE_CHARSET, outfile, errfile,
                                ctx, pool);
 }
 
Index: subversion/libsvn_diff/diff_file.c
===================================================================
--- subversion/libsvn_diff/diff_file.c	(revision 18468)
+++ subversion/libsvn_diff/diff_file.c	(working copy)
@@ -994,7 +994,7 @@
   return svn_diff_file_output_unified2(output_stream, diff,
                                        original_path, modified_path,
                                        original_header, modified_header,
-                                       APR_LOCALE_CHARSET, pool);
+                                       SVN_APR_LOCALE_CHARSET, pool);
 }
 
 
Index: subversion/libsvn_subr/cmdline.c
===================================================================
--- subversion/libsvn_subr/cmdline.c	(revision 18468)
+++ subversion/libsvn_subr/cmdline.c	(working copy)
@@ -308,7 +308,7 @@
   if (output_encoding)
     return apr_pstrdup (pool, output_encoding);
   else
-    return APR_LOCALE_CHARSET;
+    return SVN_APR_LOCALE_CHARSET;
 }
 
 int
Index: subversion/libsvn_subr/utf.c
===================================================================
--- subversion/libsvn_subr/utf.c	(revision 18468)
+++ subversion/libsvn_subr/utf.c	(working copy)
@@ -38,6 +38,12 @@
 #define SVN_UTF_NTOU_XLATE_HANDLE "svn-utf-ntou-xlate-handle"
 #define SVN_UTF_UTON_XLATE_HANDLE "svn-utf-uton-xlate-handle"
 
+#ifndef AS400
+#define SVN_APR_UTF8_CHARSET "UTF-8"
+#else
+#define SVN_APR_UTF8_CHARSET (const char*)1208
+#endif
+
 #if APR_HAS_THREADS
 static apr_thread_mutex_t *xlate_handle_mutex = NULL;
 #endif
@@ -200,15 +206,26 @@
 
   /* The error handling doesn't support the following cases, since we don't
      use them currently.  Catch this here. */
-  assert (frompage != APR_DEFAULT_CHARSET && topage != APR_DEFAULT_CHARSET
-          && (frompage != APR_LOCALE_CHARSET || topage != APR_LOCALE_CHARSET));
+#ifndef AS400
+  /* On OS400 V5R4 with UTF support, APR_DEFAULT_CHARSET and
+   * APR_LOCALE_CHARSET are both UTF-8 (CCSID 1208), so we won't get far
+   * with this assert active. */
+  assert (frompage != SVN_APR_DEFAULT_CHARSET
+          && topage != SVN_APR_DEFAULT_CHARSET
+          && (frompage != SVN_APR_LOCALE_CHARSET
+              || topage != SVN_APR_LOCALE_CHARSET));
+#endif
 
   /* Use the correct pool for creating the handle. */
   if (userdata_key && xlate_handle_hash)
     pool = apr_hash_pool_get (xlate_handle_hash);
 
   /* Try to create a handle. */
+#ifndef AS400
   apr_err = apr_xlate_open (&handle, topage, frompage, pool);
+#else
+  apr_err = apr_xlate_open (&handle, (int)topage, (int)frompage, pool);
+#endif
 
   if (APR_STATUS_IS_EINVAL (apr_err) || APR_STATUS_IS_ENOTIMPL (apr_err))
     handle = NULL;
@@ -217,6 +234,7 @@
       const char *errstr;
       /* Can't use svn_error_wrap_apr here because it calls functions in
          this file, leading to infinite recursion. */
+#ifndef AS400
       if (frompage == APR_LOCALE_CHARSET)
         errstr = apr_psprintf (pool,
                                _("Can't create a character converter from "
@@ -229,6 +247,13 @@
         errstr = apr_psprintf (pool,
                                _("Can't create a character converter from "
                                  "'%s' to '%s'"), frompage, topage);
+#else
+      /* Handle the error condition normally prevented by the assert
+       * above. */
+      errstr = apr_psprintf (pool,
+                             _("Can't create a character converter from "
+                               "'%i' to '%i'"), frompage, topage);
+#endif
       err = svn_error_create (apr_err, NULL, errstr);
       goto cleanup;
     }
@@ -449,6 +474,7 @@
 
       /* Can't use svn_error_wrap_apr here because it calls functions in
          this file, leading to infinite recursion. */
+#ifndef AS400
       if (node->frompage == APR_LOCALE_CHARSET)
         errstr = apr_psprintf
           (pool, _("Can't convert string from native encoding to '%s':"),
@@ -461,6 +487,13 @@
         errstr = apr_psprintf
           (pool, _("Can't convert string from '%s' to '%s':"),
            node->frompage, node->topage);
+#else
+      /* On OS400 V5R4 every possible node->topage and node->frompage
+       * *really* is an int. */
+      errstr = apr_psprintf
+        (pool, _("Can't convert string from CCSID '%i' to CCSID '%i'"),
+         node->frompage, node->topage);
+#endif
       err = svn_error_create (apr_err, NULL, fuzzy_escape (src_data,
                                                            src_length, pool));
       return svn_error_create (apr_err, err, errstr);