1 files changed, 14 insertions, 2 deletions
diff --git a/string.c b/string.c
index c1366e834e..af03bc72db 100644
--- a/string.c
+++ b/string.c
@@ -131,11 +131,13 @@ VALUE rb_cSymbol;
 
 #define STR_ENC_GET(str) rb_enc_from_index(ENCODING_GET(str))
 
+static int fstring_cmp(VALUE a, VALUE b);
+
 static st_table* frozen_strings;
 
 static const struct st_hash_type fstring_hash_type = {
-    rb_str_cmp,
-    rb_str_hash
+    fstring_cmp,
+    rb_str_hash,
 };
 
 VALUE
@@ -153,6 +155,16 @@ rb_fstring(VALUE str)
     return str;
 }
 
+static int
+fstring_cmp(VALUE a, VALUE b)
+{
+    int cmp = rb_str_hash_cmp(a, b);
+    if (cmp != 0) {
+	return cmp;
+    }
+    return ENCODING_GET(b) - ENCODING_GET(a);
+}
+
 static inline int
 single_byte_optimizable(VALUE str)
 {