diff --git a/string.c b/string.c
index bd4a481203..8de556718e 100644
--- a/string.c
+++ b/string.c
@@ -8727,7 +8727,7 @@ rb_str_crypt(VALUE str, VALUE salt)
 # if defined SIZEOF_CRYPT_DATA && SIZEOF_CRYPT_DATA <= 256
     struct crypt_data cdata, *const data = &cdata;
 # else
-#   undef LARGE_CRYPT_DATA
+#   define LARGE_CRYPT_DATA
     struct crypt_data *data = ALLOC(struct crypt_data);
 # endif
 #else
diff --git a/test/ruby/test_string.rb b/test/ruby/test_string.rb
index 232d92b2a3..e28dca5012 100644
--- a/test/ruby/test_string.rb
+++ b/test/ruby/test_string.rb
@@ -546,6 +546,10 @@ CODE
       assert_raise(ArgumentError) {S("mypassword").crypt(S("aa".encode(enc)))}
       assert_raise(ArgumentError) {S("mypassword".encode(enc)).crypt(S("aa"))}
     end
+
+    @cls == String and assert_no_memory_leak([], 's = ""', <<~'end;') # do
+      1000.times { s.crypt(-"..").clear  }
+    end;
   end
 
   def test_delete