diff --git a/test/tools/test_all_collections.py b/test/tools/test_all_collections.py
index 58ff2fc0e..1fbdd3e6d 100644
--- a/test/tools/test_all_collections.py
+++ b/test/tools/test_all_collections.py
@@ -21,8 +21,7 @@ def test(yamlfile_path, cxxfile_path):
     datatypes_found = []
 
     with open(cxxfile_path, mode='r', encoding="utf-8") as cxxfile:
-        for cxxline in cxxfile:
-            cxxline = cxxfile.readline()
+        for cxxline in cxxfile.readlines():
             result = re.search('insertIntoJson<edm4hep::(.+?)Collection>',
                                cxxline)
             if result: