diff --git a/fdroidserver/lint.py b/fdroidserver/lint.py
index 200bddf6..04ef0f9c 100644
--- a/fdroidserver/lint.py
+++ b/fdroidserver/lint.py
@@ -299,6 +299,8 @@ def check_bulleted_lists(app):
 
 
 def check_builds(app):
+    supported_flags = set(metadata.build_flags)
+    # needed for YAML and JSON
     for build in app.builds:
         if build.disable:
             if build.disable.startswith('Generated by import.py'):
@@ -311,6 +313,9 @@ def check_builds(app):
                 ref = srclib.split('@')[1].split('/')[0]
                 if ref.startswith(s):
                     yield "Branch '%s' used as commit in srclib '%s'" % (s, srclib)
+        for key in build.keys():
+            if key not in supported_flags:
+                yield key + ' is not an accepted build field'
 
 
 def check_files_dir(app):