Index: src/string/api.c
===================================================================
--- src/string/api.c	(revision 46399)
+++ src/string/api.c	(working copy)
@@ -2845,8 +2845,8 @@
 
 /*
 
-=item C<STRING* Parrot_str_change_charset(PARROT_INTERP, STRING *src, INTVAL
-charset_nr)>
+=item C<STRING* Parrot_str_change_charset(PARROT_INTERP, const STRING *src,
+INTVAL charset_nr)>
 
 Converts C<src> to the given charset or encoding and returns the result as a
 new string.
@@ -2859,7 +2859,7 @@
 PARROT_WARN_UNUSED_RESULT
 PARROT_CAN_RETURN_NULL
 STRING*
-Parrot_str_change_charset(PARROT_INTERP, ARGMOD_NULLOK(STRING *src),
+Parrot_str_change_charset(PARROT_INTERP, ARGIN_NULLOK(const STRING *src),
         INTVAL charset_nr)
 {
     ASSERT_ARGS(Parrot_str_change_charset)
@@ -2875,7 +2875,7 @@
                 "charset #%d not found", (int) charset_nr);
 
     if (new_charset == src->charset)
-        return src;
+        return (STRING *)src;
 
     return new_charset->to_charset(interp, src);
 }
@@ -2883,8 +2883,8 @@
 
 /*
 
-=item C<STRING* Parrot_str_change_encoding(PARROT_INTERP, STRING *src, INTVAL
-encoding_nr)>
+=item C<STRING* Parrot_str_change_encoding(PARROT_INTERP, const STRING *src,
+INTVAL encoding_nr)>
 
 Converts C<src> to the given charset or encoding and returns the result as a
 new string.
@@ -2897,7 +2897,7 @@
 PARROT_WARN_UNUSED_RESULT
 PARROT_CAN_RETURN_NULL
 STRING*
-Parrot_str_change_encoding(PARROT_INTERP, ARGMOD_NULLOK(STRING *src),
+Parrot_str_change_encoding(PARROT_INTERP, ARGIN_NULLOK(const STRING *src),
         INTVAL encoding_nr)
 {
     ASSERT_ARGS(Parrot_str_change_encoding)
@@ -2913,7 +2913,7 @@
             "encoding #%d not found", (int) encoding_nr);
 
     if (new_encoding == src->encoding)
-        return src;
+        return (STRING *)src;
 
     return new_encoding->to_encoding(interp, src);
 }
@@ -3070,7 +3070,8 @@
 
 /*
 
-=item C<PMC* Parrot_str_split(PARROT_INTERP, const STRING *delim, STRING *str)>
+=item C<PMC* Parrot_str_split(PARROT_INTERP, const STRING *delim, const STRING
+*str)>
 
 Splits the string C<str> at the delimiter C<delim>, returning a
 C<ResizableStringArray>, or his mapped type in the current HLL, of results.
@@ -3085,7 +3086,7 @@
 PARROT_CAN_RETURN_NULL
 PMC*
 Parrot_str_split(PARROT_INTERP,
-    ARGIN_NULLOK(const STRING *delim), ARGIN_NULLOK(STRING *str))
+    ARGIN_NULLOK(const STRING *delim), ARGIN_NULLOK(const STRING *str))
 {
     ASSERT_ARGS(Parrot_str_split)
     PMC    *res;
Index: include/parrot/string_funcs.h
===================================================================
--- include/parrot/string_funcs.h	(revision 46399)
+++ include/parrot/string_funcs.h	(working copy)
@@ -66,7 +66,7 @@
 PARROT_WARN_UNUSED_RESULT
 PARROT_CAN_RETURN_NULL
 STRING* Parrot_str_change_charset(PARROT_INTERP,
-    ARGMOD_NULLOK(STRING *src),
+    ARGIN_NULLOK(const STRING *src),
     INTVAL charset_nr)
         __attribute__nonnull__(1)
         FUNC_MODIFIES(*src);
@@ -75,7 +75,7 @@
 PARROT_WARN_UNUSED_RESULT
 PARROT_CAN_RETURN_NULL
 STRING* Parrot_str_change_encoding(PARROT_INTERP,
-    ARGMOD_NULLOK(STRING *src),
+    ARGIN_NULLOK(const STRING *src),
     INTVAL encoding_nr)
         __attribute__nonnull__(1)
         FUNC_MODIFIES(*src);
@@ -322,7 +322,7 @@
 PARROT_CAN_RETURN_NULL
 PMC* Parrot_str_split(PARROT_INTERP,
     ARGIN_NULLOK(const STRING *delim),
-    ARGIN_NULLOK(STRING *str))
+    ARGIN_NULLOK(const STRING *str))
         __attribute__nonnull__(1);
 
 PARROT_EXPORT