diff --git a/integration_test/integration_test.go b/integration_test/integration_test.go
index dfb719b..1f5cdd6 100644
--- a/integration_test/integration_test.go
+++ b/integration_test/integration_test.go
@@ -93,6 +93,7 @@ func (s *MySuite) TestMessageComposer() {
 	s.GenerateMessageTypesTest("testdata/ics721.json")
 	s.GenerateMessageTypesTest("testdata/dao-dao-core.json")
 	s.GenerateMessageTypesTest("testdata/axone-objectarium.json")
+	s.GenerateMessageTypesTest("testdata/map-test.json")
 }
 
 func (s *MySuite) TestQueryClient() {
@@ -106,6 +107,7 @@ func (s *MySuite) TestQueryClient() {
 	s.GenerateQueryClientTest("testdata/ics721.json")
 	s.GenerateQueryClientTest("testdata/dao-dao-core.json")
 	s.GenerateQueryClientTest("testdata/axone-objectarium.json")
+	s.GenerateQueryClientTest("testdata/map-test.json")
 }
 
 func (s *MySuite) TestInterchaintestScaffold() {
diff --git a/integration_test/testdata/map-test.json b/integration_test/testdata/map-test.json
new file mode 100644
index 0000000..a212581
--- /dev/null
+++ b/integration_test/testdata/map-test.json
@@ -0,0 +1,139 @@
+{
+  "contract_name": "map-test",
+  "contract_version": "0.0.1",
+  "idl_version": "1.0.0",
+  "instantiate": {
+    "$schema": "http://json-schema.org/draft-07/schema#",
+    "title": "InstantiateMsg",
+    "description": "Instantiate message",
+    "type": "object",
+    "additionalProperties": false
+  },
+  "execute": {
+    "$schema": "http://json-schema.org/draft-07/schema#",
+    "title": "ExecuteMsg",
+    "description": "Execute messages",
+    "oneOf": [
+      {
+        "title": "Foo",
+        "type": "object",
+        "required": [
+          "foo"
+        ],
+        "properties": {
+          "foo": {
+            "type": "object",
+            "additionalProperties": false
+          }
+        },
+        "additionalProperties": false
+      }
+    ]
+  },
+  "query": {
+    "$schema": "http://json-schema.org/draft-07/schema#",
+    "title": "QueryMsg",
+    "description": "Query messages",
+    "oneOf": [
+      {
+        "title": "MapString",
+        "type": "object",
+        "required": [
+          "map_string"
+        ],
+        "properties": {
+          "map_string": {
+            "type": "object",
+            "required": [
+              "foo"
+            ],
+            "properties": {
+              "foo": {
+                "type": "object",
+                "additionalProperties": {
+                  "type": "string"
+                }
+              }
+            },
+            "additionalProperties": false
+          }
+        },
+        "additionalProperties": false
+      },
+      {
+        "type": "object",
+        "required": [
+          "map_with_value"
+        ],
+        "properties": {
+          "map_with_value": {
+            "type": "object",
+            "required": [
+              "foo"
+            ],
+            "properties": {
+              "foo": {
+                "type": "object",
+                "additionalProperties": {
+                  "$ref": "#/definitions/Value"
+                }
+              }
+            },
+            "additionalProperties": false
+          }
+        },
+        "additionalProperties": false
+      }
+    ],
+    "definitions": {
+      "Value": {
+        "type": "object",
+        "required": [
+          "value"
+        ],
+        "properties": {
+          "value": {
+            "type": "string"
+          }
+        },
+        "additionalProperties": false
+      }
+    }
+  },
+  "migrate": null,
+  "sudo": null,
+  "responses": {
+    "map_string": {
+      "$schema": "http://json-schema.org/draft-07/schema#",
+      "title": "BarResponse",
+      "type": "object",
+      "required": [
+        "foo"
+      ],
+      "properties": {
+        "foo": {
+          "description": "The foo value",
+          "type": "string"
+        }
+      },
+      "additionalProperties": false
+    },
+    "map_with_value": {
+      "$schema": "http://json-schema.org/draft-07/schema#",
+      "title": "BarResponse",
+      "type": "object",
+      "required": [
+        "foo"
+      ],
+      "properties": {
+        "foo": {
+          "description": "The foo value",
+          "type": "string"
+        }
+      },
+      "additionalProperties": false
+    }
+  },
+  "description": "# map-test",
+  "title": "map-test"
+}
diff --git a/pkg/codegen/codegentests/cwics721_test.go b/pkg/codegen/codegentests/cwics721_test.go
index 0e267fd..e4542e0 100644
--- a/pkg/codegen/codegentests/cwics721_test.go
+++ b/pkg/codegen/codegentests/cwics721_test.go
@@ -267,8 +267,10 @@ type QueryMsg_OutgoingChannels struct {
 }
 type ExecuteMsg_ReceiveNft Cw721ReceiveMsg
 
-type ExecuteMsg_Pause struct{}
-type ExecuteMsg_Callback CallbackMsg
+type (
+	ExecuteMsg_Pause    struct{}
+	ExecuteMsg_Callback CallbackMsg
+)
 
 type ExecuteMsg_AdminCleanAndBurnNft struct {
 	ClassId    string `json:"class_id"`
diff --git a/pkg/codegen/properties.go b/pkg/codegen/properties.go
index 3afa794..9860e14 100644
--- a/pkg/codegen/properties.go
+++ b/pkg/codegen/properties.go
@@ -194,6 +194,27 @@ func getType(name string, schema *schemas.JSONSchema, required *bool, typePrefix
 			for k := range schema.Properties {
 				typeStr = strcase.ToCamel(k)
 			}
+		case schema.AdditionalProperties.JSONSchema != nil:
+			if len(schema.Properties) > 0 {
+				return "", fmt.Errorf("cannot determine the type of object %s: properties and additionalProperties are both defined", name)
+			}
+			if schema.AdditionalProperties.JSONSchema.Properties != nil {
+				return "", fmt.Errorf("cannot determine the type of object %s: a sub-object is defined in 'additionalProperties', which is currently not supported, please report this issue in https://github.com/srdtrk/go-codegen", name)
+			}
+
+			itemType, err := getType(name, schema.AdditionalProperties.JSONSchema, nil, "", false)
+			if err != nil {
+				return "", err
+			}
+
+			typeStr = "map[string]" + itemType
+			isOptional = false
+		case schema.AdditionalProperties.Bool != nil && *schema.AdditionalProperties.Bool:
+			if len(schema.Properties) > 0 {
+				return "", fmt.Errorf("cannot determine the type of object %s: properties and additionalProperties are both defined", name)
+			}
+			typeStr = "map[string]any"
+			isOptional = false
 		default:
 			return "", fmt.Errorf("cannot determine the type of object %s", name)
 		}
diff --git a/pkg/schemas/schema.go b/pkg/schemas/schema.go
index 1aa45de..50da850 100644
--- a/pkg/schemas/schema.go
+++ b/pkg/schemas/schema.go
@@ -15,7 +15,7 @@ type JSONSchema struct {
 	Required             []string               `json:"required,omitempty"`             // Section 5.15.
 	Properties           map[string]*JSONSchema `json:"properties,omitempty"`           // Section 5.16.
 	PatternProperties    map[string]*JSONSchema `json:"patternProperties,omitempty"`    // Section 5.17.
-	AdditionalProperties *bool                  `json:"additionalProperties,omitempty"` // Section 5.18.
+	AdditionalProperties *JSONSchemaOrBool      `json:"additionalProperties,omitempty"` // Section 5.18.
 	Type                 TypeList               `json:"type,omitempty"`                 // Section 5.21.
 	AllOf                []*JSONSchema          `json:"allOf,omitempty"`                // Section 5.22.
 	AnyOf                []*JSONSchema          `json:"anyOf,omitempty"`                // Section 5.23.
@@ -83,3 +83,17 @@ func (t *TypeList) UnmarshalJSON(b []byte) error {
 
 	return nil
 }
+
+// JSONSchemaOrBool represents a JSONSchema or a boolean value.
+type JSONSchemaOrBool struct {
+	JSONSchema *JSONSchema
+	Bool       *bool
+}
+
+func (t *JSONSchemaOrBool) UnmarshalJSON(b []byte) error {
+	if err := json.Unmarshal(b, &t.Bool); err == nil {
+		return nil
+	}
+	t.Bool = nil
+	return json.Unmarshal(b, &t.JSONSchema)
+}