diff --git a/tests/fuzztest/SConscript b/tests/fuzztest/SConscript
index 4aa90c4..0a00a63 100644
--- a/tests/fuzztest/SConscript
+++ b/tests/fuzztest/SConscript
@@ -89,7 +89,7 @@
 
         count += 1
 
-        maxsize = env['CPPDEFINES'].get('FUZZTEST_BUFSIZE', 256*1024)
+        maxsize = env.get('CPPDEFINES', {}).get('FUZZTEST_BUFSIZE', 256*1024)
         data_in = corpus.read(filename)[:maxsize]
 
         try: