1 files changed, 4 insertions, 3 deletions
diff --git a/ext/pathname/pathname.c b/ext/pathname/pathname.c
index bde58a3e21..84a2b5d61b 100644
--- a/ext/pathname/pathname.c
+++ b/ext/pathname/pathname.c
@@ -1,4 +1,5 @@
 #include "ruby.h"
+#include "ruby/encoding.h"
 
 static VALUE rb_cPathname;
 static ID id_at_path, id_to_path;
@@ -184,15 +185,15 @@ path_sub_ext(VALUE self, VALUE repl)
 
     StringValue(repl);
     p = RSTRING_PTR(str);
-    ext = ruby_find_extname(p, &extlen);
+    extlen = RSTRING_LEN(str);
+    ext = ruby_enc_find_extname(p, &extlen, rb_enc_get(str));
     if (ext == NULL) {
         ext = p + RSTRING_LEN(str);
     }
     else if (extlen <= 1) {
         ext += extlen;
     }
-    str2 = rb_str_dup(str);
-    rb_str_resize(str2, ext-p);
+    str2 = rb_str_subseq(str, 0, ext-p);
     rb_str_append(str2, repl);
     OBJ_INFECT(str2, str);
     return rb_class_new_instance(1, &str2, rb_obj_class(self));