diff --git a/app/models/transaction/signature_detection.rb b/app/models/transaction/signature_detection.rb
index 7f85183cb..f44a5a230 100644
--- a/app/models/transaction/signature_detection.rb
+++ b/app/models/transaction/signature_detection.rb
@@ -52,10 +52,11 @@ class Transaction::SignatureDetection
     return if !user
     return if !user.preferences
     return if !user.preferences[:signature_detection]
-    article.preferences[:signature_detection] = SignatureDetection.find_signature_line_by_article(
+    line = SignatureDetection.find_signature_line_by_article(
       user,
       article
     )
+    article.preferences[:signature_detection] = line
     article.save
   end
 
diff --git a/lib/signature_detection.rb b/lib/signature_detection.rb
index 18594b4cd..f0275bbe2 100644
--- a/lib/signature_detection.rb
+++ b/lib/signature_detection.rb
@@ -157,7 +157,7 @@ returns
 
 =end
 
-  def find_signature_line_by_article(user, article)
+  def self.find_signature_line_by_article(user, article)
     return if !user.preferences[:signature_detection]
     SignatureDetection.find_signature_line(
       user.preferences[:signature_detection],