diff --git a/mysql-test/main/json_normalize.result b/mysql-test/main/json_normalize.result
index b1363ea909959..45a8e0f6d6285 100644
--- a/mysql-test/main/json_normalize.result
+++ b/mysql-test/main/json_normalize.result
@@ -75,3 +75,152 @@ select concat_ws(' ', json_normalize(t1.text), json_normalize(t1.text)) from t1;
 concat_ws(' ', json_normalize(t1.text), json_normalize(t1.text))
 0.0E0 0.0E0
 drop table t1;
+#
+# MDEV-28922 JSON_NORMALIZE handling of duplicate keys
+#
+SET @j = '{"x": 1, "y": 2, "z": 3, "b": 0, "c": 5, "b":3, "a": 4, "b": 1, "a": 3, "a": 2, "a": 1, "b": 2}';
+SELECT @k := JSON_NORMALIZE(@j);
+@k := JSON_NORMALIZE(@j)
+{"a":1.0E0,"a":2.0E0,"a":3.0E0,"a":4.0E0,"b":0.0E0,"b":1.0E0,"b":2.0E0,"b":3.0E0,"c":5.0E0,"x":1.0E0,"y":2.0E0,"z":3.0E0}
+SELECT JSON_EXTRACT(@j, '$.b') as j1, JSON_EXTRACT(@k, '$.b') as j2;
+j1	j2
+0	0.0E0
+Primitives
+SET @j='{"a": null, "a": true, "a": false, "a": 123, "a": "string"}';
+SELECT JSON_NORMALIZE(@j);
+JSON_NORMALIZE(@j)
+{"a":"string","a":1.23E2,"a":true,"a":false,"a":null}
+SET @j2='{"a": "string", "a": 123, "a": false, "a": true, "a": null}';
+SELECT JSON_NORMALIZE(@j2);
+JSON_NORMALIZE(@j2)
+{"a":"string","a":1.23E2,"a":true,"a":false,"a":null}
+SELECT JSON_EQUALS(@j, @j2) je;
+je
+1
+Objects
+SET @j='{
+  "a": {},
+  "a": {"x":1},
+  "a": {"x":1,"y":2},
+  "a": {"x":1,"y":2,"z":3}
+}';
+SELECT JSON_NORMALIZE(@j);
+JSON_NORMALIZE(@j)
+{"a":{},"a":{"x":1.0E0},"a":{"x":1.0E0,"y":2.0E0},"a":{"x":1.0E0,"y":2.0E0,"z":3.0E0}}
+SET @j2='{
+  "a": {"x":1,"y":2,"z":3},
+  "a": {"x":1},
+  "a": {},
+  "a": {"x":1,"y":2}
+}';
+SELECT JSON_NORMALIZE(@j2);
+JSON_NORMALIZE(@j2)
+{"a":{},"a":{"x":1.0E0},"a":{"x":1.0E0,"y":2.0E0},"a":{"x":1.0E0,"y":2.0E0,"z":3.0E0}}
+SELECT JSON_EQUALS(@j, @j2) as je;
+je
+1
+Arrays
+SET @j='{
+  "a": [],
+  "a": [1],
+  "a": [1,2],
+  "a": [1,2,3],
+  "a": [1,2,3,4]
+}';
+SELECT JSON_NORMALIZE(@j);
+JSON_NORMALIZE(@j)
+{"a":[],"a":[1.0E0],"a":[1.0E0,2.0E0],"a":[1.0E0,2.0E0,3.0E0],"a":[1.0E0,2.0E0,3.0E0,4.0E0]}
+SET @j2='{
+  "a": [1,2,3],
+  "a": [],
+  "a": [1,2,3,4],
+  "a": [1],
+  "a": [1,2]
+}';
+SELECT JSON_NORMALIZE(@j2);
+JSON_NORMALIZE(@j2)
+{"a":[],"a":[1.0E0],"a":[1.0E0,2.0E0],"a":[1.0E0,2.0E0,3.0E0],"a":[1.0E0,2.0E0,3.0E0,4.0E0]}
+SELECT JSON_EQUALS(@j, @j2) je;
+je
+1
+Mixed Arrays
+SET @j='{
+  "a": [],
+  "a": [null],
+  "a": [1,"x",true],
+  "a": [{"k":1}],
+  "a": [[1,2],[3,4]]
+}';
+SELECT JSON_NORMALIZE(@j);
+JSON_NORMALIZE(@j)
+{"a":[],"a":[{"k":1.0E0}],"a":[null],"a":[[1.0E0,2.0E0],[3.0E0,4.0E0]],"a":[1.0E0,"x",true]}
+SET @j2='{
+  "a": [[1,2],[3,4]],
+  "a": [{"k":1}],
+  "a": [],
+  "a": [1,"x",true],
+  "a": [null]
+}';
+SELECT JSON_NORMALIZE(@j2);
+JSON_NORMALIZE(@j2)
+{"a":[],"a":[{"k":1.0E0}],"a":[null],"a":[[1.0E0,2.0E0],[3.0E0,4.0E0]],"a":[1.0E0,"x",true]}
+SELECT JSON_EQUALS(@j, @j2) je;
+je
+1
+Nested objects
+SET @j='{
+  "a": {"x":{"y":1}},
+  "a": {"x":{"y":[1,2]}},
+  "a": {"x":{"y":{"z":3}}},
+  "a": {"x":{}}
+}';
+SELECT JSON_NORMALIZE(@j);
+JSON_NORMALIZE(@j)
+{"a":{"x":{}},"a":{"x":{"y":{"z":3.0E0}}},"a":{"x":{"y":[1.0E0,2.0E0]}},"a":{"x":{"y":1.0E0}}}
+SET @j2='{
+  "a": {"x":{}},
+  "a": {"x":{"y":{"z":3}}},
+  "a": {"x":{"y":1}},
+  "a": {"x":{"y":[1,2]}}
+}';
+SELECT JSON_NORMALIZE(@j2);
+JSON_NORMALIZE(@j2)
+{"a":{"x":{}},"a":{"x":{"y":{"z":3.0E0}}},"a":{"x":{"y":[1.0E0,2.0E0]}},"a":{"x":{"y":1.0E0}}}
+SELECT JSON_EQUALS(@j, @j2) je;
+je
+1
+Everything mixed
+SET @j='{
+  "a": null,
+  "a": 1,
+  "a": "abc",
+  "a": true,
+  "a": [],
+  "a": [1],
+  "a": [1,2],
+  "a": {},
+  "a": {"k":1},
+  "a": {"k":1,"m":2}
+}';
+SELECT JSON_NORMALIZE(@j);
+JSON_NORMALIZE(@j)
+{"a":{},"a":{"k":1.0E0},"a":{"k":1.0E0,"m":2.0E0},"a":[],"a":[1.0E0],"a":[1.0E0,2.0E0],"a":"abc","a":1.0E0,"a":true,"a":null}
+SET @j2='{
+  "a": {"k":1},
+  "a": [],
+  "a": true,
+  "a": {"k":1,"m":2},
+  "a": "abc",
+  "a": null,
+  "a": [1,2],
+  "a": 1,
+  "a": {},
+  "a": [1]
+}';
+SELECT JSON_NORMALIZE(@j2);
+JSON_NORMALIZE(@j2)
+{"a":{},"a":{"k":1.0E0},"a":{"k":1.0E0,"m":2.0E0},"a":[],"a":[1.0E0],"a":[1.0E0,2.0E0],"a":"abc","a":1.0E0,"a":true,"a":null}
+SELECT JSON_EQUALS(@j, @j2) je;
+je
+1
+# End of 10.11 tests
diff --git a/mysql-test/main/json_normalize.test b/mysql-test/main/json_normalize.test
index 29faa514ccad0..a1c0b12026d57 100644
--- a/mysql-test/main/json_normalize.test
+++ b/mysql-test/main/json_normalize.test
@@ -56,3 +56,129 @@ select concat_ws(' ', t1.text, t1.text) from t1;
 select concat_ws(' ', json_normalize(t1.text), json_normalize(t1.text)) from t1;
 
 drop table t1;
+
+--echo #
+--echo # MDEV-28922 JSON_NORMALIZE handling of duplicate keys
+--echo #
+
+SET @j = '{"x": 1, "y": 2, "z": 3, "b": 0, "c": 5, "b":3, "a": 4, "b": 1, "a": 3, "a": 2, "a": 1, "b": 2}';
+SELECT @k := JSON_NORMALIZE(@j);
+SELECT JSON_EXTRACT(@j, '$.b') as j1, JSON_EXTRACT(@k, '$.b') as j2;
+
+--echo Primitives
+
+SET @j='{"a": null, "a": true, "a": false, "a": 123, "a": "string"}';
+SELECT JSON_NORMALIZE(@j);
+
+SET @j2='{"a": "string", "a": 123, "a": false, "a": true, "a": null}';
+SELECT JSON_NORMALIZE(@j2);
+SELECT JSON_EQUALS(@j, @j2) je;
+
+--echo Objects
+SET @j='{
+  "a": {},
+  "a": {"x":1},
+  "a": {"x":1,"y":2},
+  "a": {"x":1,"y":2,"z":3}
+}';
+SELECT JSON_NORMALIZE(@j);
+
+SET @j2='{
+  "a": {"x":1,"y":2,"z":3},
+  "a": {"x":1},
+  "a": {},
+  "a": {"x":1,"y":2}
+}';
+SELECT JSON_NORMALIZE(@j2);
+SELECT JSON_EQUALS(@j, @j2) as je;
+
+--echo Arrays
+
+SET @j='{
+  "a": [],
+  "a": [1],
+  "a": [1,2],
+  "a": [1,2,3],
+  "a": [1,2,3,4]
+}';
+SELECT JSON_NORMALIZE(@j);
+
+SET @j2='{
+  "a": [1,2,3],
+  "a": [],
+  "a": [1,2,3,4],
+  "a": [1],
+  "a": [1,2]
+}';
+SELECT JSON_NORMALIZE(@j2);
+SELECT JSON_EQUALS(@j, @j2) je;
+
+--echo Mixed Arrays
+SET @j='{
+  "a": [],
+  "a": [null],
+  "a": [1,"x",true],
+  "a": [{"k":1}],
+  "a": [[1,2],[3,4]]
+}';
+SELECT JSON_NORMALIZE(@j);
+
+SET @j2='{
+  "a": [[1,2],[3,4]],
+  "a": [{"k":1}],
+  "a": [],
+  "a": [1,"x",true],
+  "a": [null]
+}';
+SELECT JSON_NORMALIZE(@j2);
+SELECT JSON_EQUALS(@j, @j2) je;
+
+--echo Nested objects
+SET @j='{
+  "a": {"x":{"y":1}},
+  "a": {"x":{"y":[1,2]}},
+  "a": {"x":{"y":{"z":3}}},
+  "a": {"x":{}}
+}';
+SELECT JSON_NORMALIZE(@j);
+
+SET @j2='{
+  "a": {"x":{}},
+  "a": {"x":{"y":{"z":3}}},
+  "a": {"x":{"y":1}},
+  "a": {"x":{"y":[1,2]}}
+}';
+SELECT JSON_NORMALIZE(@j2);
+SELECT JSON_EQUALS(@j, @j2) je;
+
+--echo Everything mixed
+SET @j='{
+  "a": null,
+  "a": 1,
+  "a": "abc",
+  "a": true,
+  "a": [],
+  "a": [1],
+  "a": [1,2],
+  "a": {},
+  "a": {"k":1},
+  "a": {"k":1,"m":2}
+}';
+SELECT JSON_NORMALIZE(@j);
+
+SET @j2='{
+  "a": {"k":1},
+  "a": [],
+  "a": true,
+  "a": {"k":1,"m":2},
+  "a": "abc",
+  "a": null,
+  "a": [1,2],
+  "a": 1,
+  "a": {},
+  "a": [1]
+}';
+SELECT JSON_NORMALIZE(@j2);
+SELECT JSON_EQUALS(@j, @j2) je;
+
+--echo # End of 10.11 tests
diff --git a/strings/json_normalize.c b/strings/json_normalize.c
index a7849d95b3cf4..7854ecb84c02b 100644
--- a/strings/json_normalize.c
+++ b/strings/json_normalize.c
@@ -308,12 +308,93 @@ json_norm_value_string_init(struct json_norm_value *val,
 }
 
 
+static int json_norm_kv_comp(const void *a_, const void *b_);
+
+static int json_norm_value_comp(const struct json_norm_value *a,
+                                const struct json_norm_value *b)
+{
+  if (a->type != b->type)
+    return (int) a->type - b->type;
+
+  switch (a->type)
+  {
+  case JSON_VALUE_OBJECT:
+  {
+    const DYNAMIC_ARRAY *ao= &a->value.object.kv_pairs;
+    const DYNAMIC_ARRAY *bo= &b->value.object.kv_pairs;
+    int ret;
+    if (ao->elements != bo->elements)
+      return ao->elements < bo->elements ? -1 : 1;
+
+    for (size_t i= 0; i < ao->elements; ++i)
+    {
+      const struct json_norm_kv *akv=
+        dynamic_element(ao, i, struct json_norm_kv*);
+      const struct json_norm_kv *bkv=
+        dynamic_element(bo, i, struct json_norm_kv*);
+      if ((ret= json_norm_kv_comp(akv, bkv)))
+        return ret;
+    }
+    return 0;
+  }
+  case JSON_VALUE_ARRAY:
+  {
+    const DYNAMIC_ARRAY *aa= &a->value.array.values;
+    const DYNAMIC_ARRAY *ba= &b->value.array.values;
+    int ret;
+
+    if (aa->elements != ba->elements)
+      return aa->elements < ba->elements ? -1 : 1;
+
+    for (size_t i= 0; i < aa->elements; ++i)
+    {
+      const struct json_norm_value *aval=
+        dynamic_element(aa, i, struct json_norm_value*);
+      const struct json_norm_value *bval=
+        dynamic_element(ba, i, struct json_norm_value*);
+      if ((ret= json_norm_value_comp(aval, bval)))
+        return ret;
+    }
+    return 0;
+  }
+  case JSON_VALUE_STRING:
+  {
+    const LEX_STRING *as= &a->value.string;
+    const LEX_STRING *bs= &b->value.string;
+    if (as->length != bs->length)
+      return as->length < bs->length ? -1 : 1;
+
+    return my_strnncoll(&my_charset_utf8mb4_bin,
+                        (const uchar *)as->str, as->length,
+                        (const uchar *)bs->str, bs->length);
+  }
+  case JSON_VALUE_NUMBER:
+  {
+    const DYNAMIC_STRING *anum= &a->value.number;
+    const DYNAMIC_STRING *bnum= &b->value.number;
+    if (anum->length != bnum->length)
+      return anum->length < bnum->length ? -1 : 1;
+    return strncmp(anum->str, bnum->str, anum->length);
+  }
+  case JSON_VALUE_NULL:
+  case JSON_VALUE_TRUE:
+  case JSON_VALUE_FALSE:
+  case JSON_VALUE_UNINITIALIZED:
+  default:
+    return 0;
+  }
+}
+
+
 static int json_norm_kv_comp(const void *a_, const void *b_)
 {
   const struct json_norm_kv *a= a_, *b= b_;
-  return my_strnncoll(&my_charset_utf8mb4_bin,
-                      (const uchar *)a->key.str, a->key.length,
-                      (const uchar *)b->key.str, b->key.length);
+  int ret;
+  if (!(ret= my_strnncoll(&my_charset_utf8mb4_bin,
+                          (const uchar *)a->key.str, a->key.length,
+                          (const uchar *)b->key.str, b->key.length)))
+    return json_norm_value_comp(&a->value, &b->value);
+  return ret;
 }