diff --git a/datamodel/high/base/schema_proxy.go b/datamodel/high/base/schema_proxy.go
index 701e5f6..54cd1ff 100644
--- a/datamodel/high/base/schema_proxy.go
+++ b/datamodel/high/base/schema_proxy.go
@@ -76,7 +76,7 @@ func CreateSchemaProxyRef(ref string) *SchemaProxy {
 // If there is a problem building the Schema, then this method will return nil. Use GetBuildError to gain access
 // to that building error.
 func (sp *SchemaProxy) Schema() *Schema {
-	if sp == nil {
+	if sp == nil || sp.lock == nil {
 		return nil
 	}
 	sp.lock.Lock()
diff --git a/datamodel/high/base/schema_proxy_test.go b/datamodel/high/base/schema_proxy_test.go
index 46dcac6..51ebac1 100644
--- a/datamodel/high/base/schema_proxy_test.go
+++ b/datamodel/high/base/schema_proxy_test.go
@@ -60,6 +60,11 @@ func TestSchemaProxy_MarshalYAML(t *testing.T) {
 	assert.Equal(t, "$ref: '#/components/schemas/nice'", strings.TrimSpace(string(rend)))
 }
 
+func TestCreateSchemaProxy_Fail(t *testing.T) {
+	proxy := &SchemaProxy{}
+	assert.Nil(t, proxy.Schema())
+}
+
 func TestCreateSchemaProxy(t *testing.T) {
 	sp := CreateSchemaProxy(&Schema{Description: "iAmASchema"})
 	assert.Equal(t, "iAmASchema", sp.rendered.Description)
diff --git a/document_test.go b/document_test.go
index b8c3e4f..0d90764 100644
--- a/document_test.go
+++ b/document_test.go
@@ -59,6 +59,13 @@ definitions:
 	assert.Nil(t, v2Doc)
 }
 
+func TestLoadDocument_WrongDoc(t *testing.T) {
+	yml := `IAmNotAnOpenAPI: 3.1.0`
+	doc, err := NewDocument([]byte(yml))
+	assert.Error(t, err)
+	assert.Nil(t, doc)
+}
+
 func TestLoadDocument_Simple_V3_Error(t *testing.T) {
 	yml := `openapi: 3.0.1`
 	doc, err := NewDocument([]byte(yml))