diff --git a/PKG-INFO b/PKG-INFO
index d32ec1c75daab61a182ea73fadc761ef17c01594..f0a6d7d6146ff5af350c267bb615f22127d353bf 100644
--- a/PKG-INFO
+++ b/PKG-INFO
@@ -1,6 +1,6 @@
 Metadata-Version: 2.1
 Name: swh.model
-Version: 0.0.55
+Version: 0.0.56
 Summary: Software Heritage data model
 Home-page: https://forge.softwareheritage.org/diffusion/DMOD/
 Author: Software Heritage developers
diff --git a/swh.model.egg-info/PKG-INFO b/swh.model.egg-info/PKG-INFO
index d32ec1c75daab61a182ea73fadc761ef17c01594..f0a6d7d6146ff5af350c267bb615f22127d353bf 100644
--- a/swh.model.egg-info/PKG-INFO
+++ b/swh.model.egg-info/PKG-INFO
@@ -1,6 +1,6 @@
 Metadata-Version: 2.1
 Name: swh.model
-Version: 0.0.55
+Version: 0.0.56
 Summary: Software Heritage data model
 Home-page: https://forge.softwareheritage.org/diffusion/DMOD/
 Author: Software Heritage developers
diff --git a/swh/model/hypothesis_strategies.py b/swh/model/hypothesis_strategies.py
index 8d3923c76536fe7f0888b7e8be14693f9002f6a9..e6d830aa111f1c59d8fcba255326b463534b8dd6 100644
--- a/swh/model/hypothesis_strategies.py
+++ b/swh/model/hypothesis_strategies.py
@@ -26,6 +26,10 @@ pgsql_alphabet = characters(
     blacklist_characters=['\u0000'])  # postgresql does not like these
 
 
+def optional(strategy):
+    return one_of(none(), strategy)
+
+
 def pgsql_text():
     return text(alphabet=pgsql_alphabet)
 
@@ -81,7 +85,8 @@ def origin_visits():
         visit=integers(0, 1000),
         origin=urls(),
         status=sampled_from(['ongoing', 'full', 'partial']),
-        type=pgsql_text())
+        type=pgsql_text(),
+        snapshot=optional(sha1_git()))
 
 
 @composite
@@ -148,9 +153,6 @@ def present_contents(draw):
 
 @composite
 def skipped_contents(draw):
-    def optional(strategy):
-        return one_of(none(), strategy)
-
     return draw(builds(
         SkippedContent,
         length=integers(min_value=-1, max_value=2**63-1),
diff --git a/swh/model/model.py b/swh/model/model.py
index 2a2eda27e398bc3c38242f620064f0e27167a048..512824d60a1ab05254dbb7649d6f0ba2ffc54bd6 100644
--- a/swh/model/model.py
+++ b/swh/model/model.py
@@ -149,7 +149,7 @@ class OriginVisit(BaseModel):
         type=str,
         validator=attr.validators.in_(['ongoing', 'full', 'partial']))
     type = attr.ib(type=str)
-    snapshot = attr.ib(type=Sha1Git)
+    snapshot = attr.ib(type=Optional[Sha1Git])
     metadata = attr.ib(type=Optional[Dict[str, object]],
                        default=None)
 
diff --git a/version.txt b/version.txt
index 8c5743b4feeccce19dee1a30d4bdd0e9413b8064..fc9120ade4f5e100bf204c973fc37610cb316167 100644
--- a/version.txt
+++ b/version.txt
@@ -1 +1 @@
-v0.0.55-0-g73053a6
\ No newline at end of file
+v0.0.56-0-gfcfbd4d
\ No newline at end of file