diff --git a/swh/web/common/service.py b/swh/web/common/service.py
--- a/swh/web/common/service.py
+++ b/swh/web/common/service.py
@@ -89,6 +89,7 @@
     """
     algo, hash = query.parse_hash(q)
     found = storage.content_find({algo: hash})
+    found = found[0] if found else None
     return {'found': converters.from_content(found),
             'algo': algo}
 
@@ -104,7 +105,7 @@
     """
     algo, hash = query.parse_hash(q)
     found = storage.content_find({algo: hash})
-    return {'found': found is not None}
+    return {'found': bool(found)}
 
 
 def _lookup_content_sha1(q):
@@ -122,7 +123,7 @@
         hashes = storage.content_find({algo: hash})
         if not hashes:
             return None
-        return hashes['sha1']
+        return hashes[0]['sha1']
     return hash
 
 
@@ -718,6 +719,12 @@
                                     directory_entries))}
     elif entity['type'] == 'file':  # content
         content = storage.content_find({'sha1_git': entity['target']})
+        content = content[0] if content else None
+        if not content:
+            raise NotFoundExc(
+                "Content not found with revision '%s' "
+                % (entity['target'])
+            )
         if with_data:
             c = _first_element(storage.content_get([content['sha1']]))
             content['data'] = c['data']
@@ -751,7 +758,7 @@
     if not c:
         raise NotFoundExc('Content with %s checksum equals to %s not found!' %
                           (algo, hashutil.hash_to_hex(hash)))
-    return converters.from_content(c)
+    return converters.from_content(c[0])
 
 
 def lookup_content_raw(q):
diff --git a/swh/web/tests/common/test_service.py b/swh/web/tests/common/test_service.py
--- a/swh/web/tests/common/test_service.py
+++ b/swh/web/tests/common/test_service.py
@@ -340,8 +340,19 @@
         self.assertIn('Revision %s not found' % unknown_revision,
                       cm.exception.args[0])
 
+    @given(unknown_content())
+    def test_lookup_directory_with_revision_unknown_content(
+            self, unknown_content):
+        sha1_git = unknown_content['sha1_git']
+
+        with self.assertRaises(NotFoundExc) as cm:
+            service.lookup_directory_with_revision(sha1_git)
+        self.assertIn('Content not found for %s' % sha1_git,
+                      cm.exception.args[0])
+
     @given(revision())
-    def test_lookup_directory_with_revision_ko_path_to_nowhere(self, revision):
+    def test_lookup_directory_with_revision_ko_path_to_nowhere(
+            self, revision):
 
         invalid_path = 'path/to/something/unknown'
         with self.assertRaises(NotFoundExc) as cm: