diff --git a/src/MiniDocs/Markdown.class.st b/src/MiniDocs/Markdown.class.st
index cf759c4..1696097 100644
--- a/src/MiniDocs/Markdown.class.st
+++ b/src/MiniDocs/Markdown.class.st
@@ -159,7 +159,8 @@ Markdown >> fromFile: aFileReference [
 
 { #category : #'instance creation' }
 Markdown >> fromString: markdownString [
-	(self metadata) at: 'original' put: markdownString yamlMetadata.
+	markdownString yamlMetadata 
+		ifNotNil: [(self metadata) at: 'original' put: markdownString yamlMetadata].
 	self body: markdownString contentsWithoutYAMLMetadata
 ]
 
diff --git a/src/MiniDocs/String.extension.st b/src/MiniDocs/String.extension.st
index 7ec24cb..a619ac6 100644
--- a/src/MiniDocs/String.extension.st
+++ b/src/MiniDocs/String.extension.st
@@ -118,6 +118,7 @@ String >> withoutXMLTagDelimiters [
 
 { #category : #'*MiniDocs' }
 String >> yamlMetadata [
+	self yamlMetadataString ifNil: [^ nil ].
 	^ (YAML2JSON fromString: self yamlMetadataString) 
 ]