diff --git a/swh/indexer/storage/__init__.py b/swh/indexer/storage/__init__.py
--- a/swh/indexer/storage/__init__.py
+++ b/swh/indexer/storage/__init__.py
@@ -442,7 +442,7 @@
             yield converters.db_to_ctags(dict(zip(db.content_ctags_cols, obj)))
 
     @remote_api_endpoint('content/fossology_license')
-    @db_transaction_generator()
+    @db_transaction()
     def content_fossology_license_get(self, ids, db=None, cur=None):
         """Retrieve licenses per id.
 
@@ -450,8 +450,8 @@
             ids (iterable): sha1 checksums
 
         Yields:
-            dict: ``{id: facts}`` where ``facts`` is a dict with the
-            following keys:
+            dict: ``{id: facts}`` where ``facts`` is a list of
+            dicts with the following keys:
 
                 - **licenses** ([str]): associated licenses for that content
                 - **tool** (dict): Tool used to compute the license
@@ -464,8 +464,7 @@
             id_ = license['id']
             d[id_].append(converters.db_to_fossology_license(license))
 
-        for id_, facts in d.items():
-            yield {id_: facts}
+        return d
 
     @remote_api_endpoint('content/fossology_license/add')
     @db_transaction()
diff --git a/swh/indexer/storage/in_memory.py b/swh/indexer/storage/in_memory.py
--- a/swh/indexer/storage/in_memory.py
+++ b/swh/indexer/storage/in_memory.py
@@ -435,11 +435,10 @@
         # the new one. SubStorage.get should be updated once all other
         # *_get methods use the new format.
         # See: https://forge.softwareheritage.org/T1433
-        res = {}
+        res = defaultdict(list)
         for d in self._licenses.get(ids):
-            res.setdefault(d.pop('id'), []).append(d)
-        for (id_, facts) in res.items():
-            yield {id_: facts}
+            res[d.pop('id')].append(d)
+        return res
 
     def content_fossology_license_add(self, licenses, conflict_update=False):
         """Add licenses not present in storage.
diff --git a/swh/indexer/tests/storage/test_storage.py b/swh/indexer/tests/storage/test_storage.py
--- a/swh/indexer/tests/storage/test_storage.py
+++ b/swh/indexer/tests/storage/test_storage.py
@@ -884,8 +884,8 @@
         self.storage.content_fossology_license_add([license_v1])
 
         # when
-        actual_licenses = list(self.storage.content_fossology_license_get(
-            [self.sha1_1]))
+        actual_licenses = self.storage.content_fossology_license_get(
+            [self.sha1_1])
 
         # then
         expected_license = {
@@ -904,8 +904,8 @@
 
         self.storage.content_fossology_license_add([license_v2])
 
-        actual_licenses = list(self.storage.content_fossology_license_get(
-            [self.sha1_1]))
+        actual_licenses = self.storage.content_fossology_license_get(
+            [self.sha1_1])
 
         expected_license = {
             self.sha1_1: [{