diff --git a/infra/gcb/build.py b/infra/gcb/build.py
index eecb43622..b966c2075 100755
--- a/infra/gcb/build.py
+++ b/infra/gcb/build.py
@@ -38,6 +38,7 @@ def load_project_yaml(project_dir):
     project_yaml.setdefault('name', project_name)
     project_yaml.setdefault('image', 
         'gcr.io/clusterfuzz-external/oss-fuzz/' + project_name)
+    project_yaml.setdefault('sanitizers', DEFAULT_SANITIZERS)
     return project_yaml
 
 
@@ -66,8 +67,7 @@ def get_build_steps(project_yaml):
           },
     ]
 
-  sanitizers = project_yaml.get('sanitizers', DEFAULT_SANITIZERS)
-  for sanitizer in sanitizers:
+  for sanitizer in project_yaml['sanitizers']:
     env = CONFIGURATIONS["sanitizer-" + sanitizer]
     out = '/workspace/out/' + sanitizer
     zip_file = name + "-" + sanitizer + "-" + ts + ".zip"