diff --git a/openapi3/mapping_test.go b/openapi3/mapping_test.go
new file mode 100644
index 00000000..0c1c1995
--- /dev/null
+++ b/openapi3/mapping_test.go
@@ -0,0 +1,58 @@
+package openapi3
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestMapping(t *testing.T) {
+
+	schema := `
+openapi: 3.0.0
+info:
+  title: ACME
+  version: 1.0.0
+components:
+  schemas:
+    Pet:
+      type: object
+      required:
+      - petType
+      properties:
+        petType:
+          type: string
+      discriminator:
+        propertyName: petType
+        mapping:
+          dog: Dog
+    Cat:
+      allOf:
+      - $ref: '#/components/schemas/Pet'
+      - type: object
+        # all other properties specific to a Cat
+        properties:
+          name:
+            type: string
+    Dog:
+      allOf:
+      - $ref: '#/components/schemas/Pet'
+      - type: object
+        # all other properties specific to a Dog
+        properties:
+          bark:
+            type: string
+    Lizard:
+      allOf:
+      - $ref: '#/components/schemas/Pet'
+      - type: object
+        # all other properties specific to a Lizard
+        properties:
+          lovesRocks:
+            type: boolean
+`
+	loader := NewLoader()
+	loader.IsExternalRefsAllowed = true
+	_, err := loader.LoadFromData([]byte(schema))
+	require.NoError(t, err)
+}