1 files changed, 1 insertions, 1 deletions
diff --git a/check.py b/check.py
index 5c42c8812..105c177c7 100755
--- a/check.py
+++ b/check.py
@@ -78,7 +78,7 @@ for t in sorted(os.listdir(os.path.join(options.binaryen_test, 'passes'))):
     print '..', t
     binary = '.wasm' in t
     passname = os.path.basename(t).replace('.wast', '').replace('.wasm', '')
-    opts = ['-' + passname] if passname.startswith('O') else ['--' + p for p in passname.split('_')]
+    opts = [('--' + p if not p.startswith('O') else '-' + p) for p in passname.split('_')]
     t = os.path.join(options.binaryen_test, 'passes', t)
     actual = ''
     for module, asserts in split_wast(t):