diff --git a/spec/spec.go b/spec/spec.go
index e1a7fae5..40591324 100644
--- a/spec/spec.go
+++ b/spec/spec.go
@@ -133,6 +133,8 @@ func (s *Schema) UnmarshalJSON(data []byte) error {
 		return err
 	}
 
+	additionalPropertiesValue := rawFields["additionalProperties"]
+
 	for _, supportedField := range supportedSchemaFields {
 		delete(rawFields, supportedField)
 	}
@@ -153,7 +155,6 @@ func (s *Schema) UnmarshalJSON(data []byte) error {
 	}
 	*s = Schema(inner)
 
-	additionalPropertiesValue := rawFields["additional_properties"]
 	additionalPropertiesBool, ok := additionalPropertiesValue.(bool)
 
 	// AdditionalProperties can be a `false` or `Schema` object for convenience turn
diff --git a/spec/spec_test.go b/spec/spec_test.go
index 5691be32..da6e297f 100644
--- a/spec/spec_test.go
+++ b/spec/spec_test.go
@@ -15,6 +15,52 @@ func TestUnmarshal_Simple(t *testing.T) {
 	assert.Equal(t, "string", schema.Type)
 }
 
+func TestUnmarshal_ObjectWithAdditionalProperties(t *testing.T) {
+	data := []byte(`{
+		"type": "object",
+		"additionalProperties": {
+			"properties": {
+				"prop": {
+					"type": "number"
+				}
+			},
+			"type": "object"
+		}
+	}`)
+	var schema Schema
+	err := json.Unmarshal(data, &schema)
+	assert.NoError(t, err)
+	assert.Equal(t, "object", schema.Type)
+	assert.True(t, schema.AdditionalPropertiesAllowed)
+	assert.Equal(t, "object", schema.AdditionalProperties.Type)
+	assert.Equal(t, 1, len(schema.AdditionalProperties.Properties))
+}
+
+func TestUnmarshal_ObjectWithAdditionalPropertiesFalse(t *testing.T) {
+	data := []byte(`{
+		"type": "object",
+		"additionalProperties": false
+	}`)
+	var schema Schema
+	err := json.Unmarshal(data, &schema)
+	assert.NoError(t, err)
+	assert.Equal(t, "object", schema.Type)
+	assert.False(t, schema.AdditionalPropertiesAllowed)
+	assert.Nil(t, schema.AdditionalProperties)
+}
+
+func TestUnmarshal_ObjectWithAdditionalPropertiesDefault(t *testing.T) {
+	data := []byte(`{
+		"type": "object"
+	}`)
+	var schema Schema
+	err := json.Unmarshal(data, &schema)
+	assert.NoError(t, err)
+	assert.Equal(t, "object", schema.Type)
+	assert.True(t, schema.AdditionalPropertiesAllowed)
+	assert.Nil(t, schema.AdditionalProperties)
+}
+
 func TestUnmarshal_UnsupportedField(t *testing.T) {
 	// We don't support 'const'
 	data := []byte(`{const: "hello"}`)