diff --git a/src/json.c b/src/json.c
index fd1b6ec..e5e85eb 100644
--- a/src/json.c
+++ b/src/json.c
@@ -863,7 +863,7 @@
 		    && cur_item != NULL)
 	    {
 		top_item->jd_key = get_tv_string_buf_chk(cur_item, key_buf);
-		if (top_item->jd_key == NULL || *top_item->jd_key == NUL)
+		if (top_item->jd_key == NULL)
 		{
 		    clear_tv(cur_item);
 		    EMSG(_(e_invarg));
diff --git a/src/testdir/test_json.vim b/src/testdir/test_json.vim
index 6616365..6c3d16c 100644
--- a/src/testdir/test_json.vim
+++ b/src/testdir/test_json.vim
@@ -144,6 +144,11 @@
   call assert_equal(type(v:none), type(json_decode('')))
   call assert_equal("", json_decode('""'))
 
+  " empty key is OK
+  call assert_equal({'': 'ok'}, json_decode('{"": "ok"}'))
+  " but not twice
+  call assert_fails("call json_decode('{\"\": \"ok\", \"\": \"bad\"}')", 'E938:')
+
   call assert_equal({'n': 1}, json_decode('{"n":1,}'))
   call assert_fails("call json_decode(\"{'n':'1',}\")", 'E474:')
   call assert_fails("call json_decode(\"'n'\")", 'E474:')
diff --git a/src/version.c b/src/version.c
index 83e3b53..dbe0dcb 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    309,
+/**/
     308,
 /**/
     307,