diff --git a/bin/tests/system/ixfr/tests.sh b/bin/tests/system/ixfr/tests.sh
index 508e6f511d..ff4c16cbfb 100644
--- a/bin/tests/system/ixfr/tests.sh
+++ b/bin/tests/system/ixfr/tests.sh
@@ -243,7 +243,7 @@ $DIG $DIGOPTS test.nil. TXT @10.53.0.1 >dig.out.test$n.2 || ret=1
 grep -q -F "serial 4, fallback AXFR" dig.out.test$n.2 || ret=1
 
 # Ensure the expected error is logged.
-nextpart ns1/named.run | grep -q -F "SOA name mismatch" || ret=1
+nextpart ns1/named.run | grep -F "SOA name mismatch" >/dev/null || ret=1
 
 if [ $ret != 0 ]; then echo_i "failed"; fi
 status=$((status + ret))
diff --git a/bin/tests/system/rpz/tests.sh b/bin/tests/system/rpz/tests.sh
index 917887ebca..87e4118ca3 100644
--- a/bin/tests/system/rpz/tests.sh
+++ b/bin/tests/system/rpz/tests.sh
@@ -622,7 +622,7 @@ nochange_ns10 a3-1.static-stub-nomatch # 16
 if [ "$MODE" = dnsrps ]; then
   addr 12.12.12.12 as-ns.tld5. # 17 qname-as-ns
 fi
-nextpart ns3/named.run | grep -q "unrecognized NS rpz_rrset_find() failed: glue" \
+nextpart ns3/named.run | grep -F "unrecognized NS rpz_rrset_find() failed: glue" >/dev/null \
   && setret "seen: unrecognized NS rpz_rrset_find() failed: glue"
 end_group
 if [ "$MODE" = dnsrps ]; then
@@ -645,7 +645,7 @@ nochange_ns10 a4-1.static-stub-nomatch # 8
 if [ "$MODE" = dnsrps ]; then
   addr 12.12.12.12 as-ns.tld5. # 9 ip-as-ns
 fi
-nextpart ns3/named.run | grep -q "unrecognized NS rpz_rrset_find() failed: glue" \
+nextpart ns3/named.run | grep -F "unrecognized NS rpz_rrset_find() failed: glue" >/dev/null \
   && setret "seen: unrecognized NS rpz_rrset_find() failed: glue"
 end_group