1 files changed, 3 insertions, 1 deletions
diff --git a/string.c b/string.c
index 9466b4b33c..4de0954a46 100644
--- a/string.c
+++ b/string.c
@@ -471,6 +471,8 @@ rb_str_format_m(str, arg)
     return rb_str_format(1, &arg, str);
 }
 
+static const char null_str[] = "";
+
 static int
 str_independent(str)
     VALUE str;
@@ -481,6 +483,7 @@ str_independent(str)
     if (OBJ_FROZEN(str)) rb_error_frozen("string");
     if (!OBJ_TAINTED(str) && rb_safe_level() >= 4)
 	rb_raise(rb_eSecurityError, "Insecure: can't modify string");
+    if (RSTRING(str)->ptr == null_str) return 0;
     if (!FL_TEST(str, ELTS_SHARED)) return 1;
     return 0;
 }
@@ -539,7 +542,6 @@ rb_str_associated(str)
     return Qfalse;
 }
 
-static const char null_str[] = "";
 #define make_null_str(s) do { \
 	FL_SET(s, ELTS_SHARED); \
 	RSTRING(s)->ptr = (char *)null_str; \