diff --git a/openapi2conv/openapi2_conv.go b/openapi2conv/openapi2_conv.go
index 53b4b40cc..8c082053f 100644
--- a/openapi2conv/openapi2_conv.go
+++ b/openapi2conv/openapi2_conv.go
@@ -485,6 +485,16 @@ func ToV3SchemaRef(schema *openapi3.SchemaRef) *openapi3.SchemaRef {
 	for i, v := range schema.Value.AllOf {
 		schema.Value.AllOf[i] = ToV3SchemaRef(v)
 	}
+	if val, ok := schema.Value.Extensions["x-nullable"]; ok {
+		var nullable bool
+
+		if err := json.Unmarshal(val.(json.RawMessage), &nullable); err == nil {
+			schema.Value.Nullable = nullable
+		}
+
+		delete(schema.Value.Extensions, "x-nullable")
+	}
+
 	return schema
 }
 
@@ -824,6 +834,11 @@ func FromV3SchemaRef(schema *openapi3.SchemaRef, components *openapi3.Components
 	for i, v := range schema.Value.AllOf {
 		schema.Value.AllOf[i], _ = FromV3SchemaRef(v, components)
 	}
+	if schema.Value.Nullable {
+		schema.Value.Nullable = false
+		schema.Value.Extensions["x-nullable"] = true
+	}
+
 	return schema, nil
 }
 
diff --git a/openapi2conv/openapi2_conv_test.go b/openapi2conv/openapi2_conv_test.go
index 9edce54de..317772152 100644
--- a/openapi2conv/openapi2_conv_test.go
+++ b/openapi2conv/openapi2_conv_test.go
@@ -89,7 +89,8 @@ const exampleV2 = `
 			"additionalProperties": true,
 			"properties": {
 				"foo": {
-					"type": "string"
+					"type": "string",
+					"x-nullable": true
 				},
 				"quux": {
 					"$ref": "#/definitions/ItemExtension"
@@ -463,7 +464,8 @@ const exampleV3 = `
 				"additionalProperties": true,
 				"properties": {
 					"foo": {
-						"type": "string"
+						"type": "string",
+						"nullable": true
 					},
 					"quux": {
 						"$ref": "#/components/schemas/ItemExtension"