diff --git a/fuzzers/030-iob18/Makefile b/fuzzers/030-iob18/Makefile
index f90dbfd95..952cefd67 100644
--- a/fuzzers/030-iob18/Makefile
+++ b/fuzzers/030-iob18/Makefile
@@ -5,7 +5,7 @@
 # https://opensource.org/licenses/ISC
 #
 # SPDX-License-Identifier: ISC
-N := 80
+N := 40
 SPECIMENS_DEPS := build/iobanks.txt
 include ../fuzzer.mk
 
@@ -23,6 +23,8 @@ build/segbits_riob18.db: build/segbits_riob18.rdb process_rdb.py bits.dbf
 	sed '/IOB18.IOB_Y1.LVDS/d' -i build/segbits_riob18.rdb
 	python3 process_rdb.py build/segbits_riob18.rdb > build/segbits_riob18_processed.rdb
 	${XRAY_DBFIXUP} --db-root build --zero-db bits.dbf --groups tag_groups.txt --seg-fn-in build/segbits_riob18_processed.rdb --seg-fn-out $@
+	echo 'RIOB18.IOB_Y0.SSTL12_SSTL135_SSTL15.IN !38_126 39_127' >> $@
+	sort -o $@ $@
 	${XRAY_MASKMERGE} build/mask_riob18.db $$(find -name segdata_riob18.txt)
 
 build/segbits_hclk_ioi.rdb: $(SPECIMENS_OK)