diff --git a/fuzzers/012-clbn5ffmux/generate.sh b/fuzzers/012-clbn5ffmux/generate.sh
index d272452b..93c44166 100644
--- a/fuzzers/012-clbn5ffmux/generate.sh
+++ b/fuzzers/012-clbn5ffmux/generate.sh
@@ -8,6 +8,7 @@ set -ex
 
 python3 ../top.py >top.v
 vivado -mode batch -source ../generate.tcl
+test -z $(fgrep CRITICAL vivado.log)
 
 for x in design*.bit; do
 	../../../build/tools/bitread -F $XRAY_ROI_FRAMES -o ${x}s -z -y $x