diff --git a/tests/test_benchmark.py b/tests/test_benchmark.py
index a0edc4bf78e07..8b204a0143a56 100644
--- a/tests/test_benchmark.py
+++ b/tests/test_benchmark.py
@@ -215,7 +215,7 @@ def build(self, parent, filename, args, shared_args, emcc_args, native_args, nat
     # add additional emcc args at the end, which may override other things
     # above, such as minimal runtime
     cmd += emcc_args + self.extra_args
-    if 'FORCE_FILESYSTEM' not in cmd:
+    if '-sFORCE_FILESYSTEM' not in cmd:
       cmd += ['-sFILESYSTEM=0']
     if PROFILING:
       cmd += ['--profiling-funcs']