diff --git a/mayan/apps/document_signatures/models.py b/mayan/apps/document_signatures/models.py
index f80b3ce640..a1a1933923 100644
--- a/mayan/apps/document_signatures/models.py
+++ b/mayan/apps/document_signatures/models.py
@@ -19,7 +19,7 @@ class DocumentVersionSignature(models.Model):
     Model that describes a document version signature properties
     """
     document_version = models.ForeignKey(DocumentVersion, verbose_name=_(u'Document version'), editable=False)
-    signature_file = models.FileField(blank=True, null=True, upload_to=lambda: UUID_FUNCTION(), storage=storage_backend, verbose_name=_(u'Signature file'), editable=False)
+    signature_file = models.FileField(blank=True, null=True, upload_to=lambda instance, filename: UUID_FUNCTION(), storage=storage_backend, verbose_name=_(u'Signature file'), editable=False)
     has_embedded_signature = models.BooleanField(default=False, verbose_name=_(u'Has embedded signature'), editable=False)
 
     objects = DocumentVersionSignatureManager()
diff --git a/mayan/apps/documents/models.py b/mayan/apps/documents/models.py
index 0ad1cdebba..d81f7f61ec 100644
--- a/mayan/apps/documents/models.py
+++ b/mayan/apps/documents/models.py
@@ -313,7 +313,7 @@ class DocumentVersion(models.Model):
     comment = models.TextField(blank=True, verbose_name=_(u'Comment'))
 
     # File related fields
-    file = models.FileField(upload_to=lambda: UUID_FUNCTION(), storage=storage_backend, verbose_name=_(u'File'))
+    file = models.FileField(upload_to=lambda instance, filename: UUID_FUNCTION(), storage=storage_backend, verbose_name=_(u'File'))
     mimetype = models.CharField(max_length=255, null=True, blank=True, editable=False)
     encoding = models.CharField(max_length=64, null=True, blank=True, editable=False)