diff --git a/swh/graphql/resolvers/release.py b/swh/graphql/resolvers/release.py
--- a/swh/graphql/resolvers/release.py
+++ b/swh/graphql/resolvers/release.py
@@ -15,7 +15,7 @@
     """
 
     def _get_release_by_id(self, release_id):
-        return (self.archive.get_releases([release_id]) or None)[0]
+        return self.archive.get_releases([release_id])[0]
 
     @property
     def target_hash(self):
diff --git a/swh/graphql/resolvers/revision.py b/swh/graphql/resolvers/revision.py
--- a/swh/graphql/resolvers/revision.py
+++ b/swh/graphql/resolvers/revision.py
@@ -22,7 +22,7 @@
     """
 
     def _get_revision_by_id(self, revision_id):
-        return (self.archive.get_revisions([revision_id]) or None)[0]
+        return self.archive.get_revisions([revision_id])[0]
 
     @property
     def parent_swhids(self):  # for ParentRevisionConnection resolver
diff --git a/swh/graphql/tests/functional/test_content.py b/swh/graphql/tests/functional/test_content.py
--- a/swh/graphql/tests/functional/test_content.py
+++ b/swh/graphql/tests/functional/test_content.py
@@ -161,3 +161,15 @@
         "length": 4,
         "swhid": "swh:1:cnt:86bc6b377e9d25f9d26777a4a28d08e63e7c5779",
     }
+
+
+def test_get_content_with_unknown_swhid(client):
+    unknown_sha1 = "1" * 40
+    query_str = """
+    {
+      content(swhid: "swh:1:cnt:%s") {
+        swhid
+      }
+    }
+    """
+    utils.assert_missing_object(client, query_str % unknown_sha1, "content")
diff --git a/swh/graphql/tests/functional/test_directory.py b/swh/graphql/tests/functional/test_directory.py
--- a/swh/graphql/tests/functional/test_directory.py
+++ b/swh/graphql/tests/functional/test_directory.py
@@ -72,3 +72,15 @@
     assert data["release"]["target"] == {
         "swhid": "swh:1:dir:0505050505050505050505050505050505050505"
     }
+
+
+def test_get_directory_with_unknown_swhid(client):
+    unknown_sha1 = "1" * 40
+    query_str = """
+    {
+      directory(swhid: "swh:1:dir:%s") {
+        swhid
+      }
+    }
+    """
+    utils.assert_missing_object(client, query_str % unknown_sha1, "directory")
diff --git a/swh/graphql/tests/functional/test_release_node.py b/swh/graphql/tests/functional/test_release_node.py
--- a/swh/graphql/tests/functional/test_release_node.py
+++ b/swh/graphql/tests/functional/test_release_node.py
@@ -75,7 +75,7 @@
 def test_get_release_with_invalid_swhid(client):
     query_str = """
     {
-      content(swhid: "swh:1:rel:invalid") {
+      release(swhid: "swh:1:rel:invalid") {
         swhid
       }
     }
@@ -163,3 +163,15 @@
         },
         "targetType": "revision",
     }
+
+
+def test_get_release_with_unknown_swhid(client):
+    unknown_sha1 = "1" * 40
+    query_str = """
+    {
+      release(swhid: "swh:1:rel:%s") {
+        swhid
+      }
+    }
+    """
+    utils.assert_missing_object(client, query_str % unknown_sha1, "release")
diff --git a/swh/graphql/tests/functional/test_revision.py b/swh/graphql/tests/functional/test_revision.py
--- a/swh/graphql/tests/functional/test_revision.py
+++ b/swh/graphql/tests/functional/test_revision.py
@@ -158,3 +158,15 @@
             {"swhid": str(get_revisions()[1].swhid())},
         ]
     }
+
+
+def test_get_revision_with_unknown_swhid(client):
+    unknown_sha1 = "1" * 40
+    query_str = """
+    {
+      revision(swhid: "swh:1:rev:%s") {
+        swhid
+      }
+    }
+    """
+    utils.assert_missing_object(client, query_str % unknown_sha1, "revision")
diff --git a/swh/graphql/tests/functional/utils.py b/swh/graphql/tests/functional/utils.py
--- a/swh/graphql/tests/functional/utils.py
+++ b/swh/graphql/tests/functional/utils.py
@@ -23,6 +23,7 @@
     assert data[obj_type] is None
     assert len(errors) == 1
     assert errors[0]["message"] == "Object error: Requested object is not available"
+    assert errors[0]["path"] == [obj_type]
 
 
 def get_error_response(client, query_str: str, error_code: int = 400) -> Dict: