diff --git a/bin/tests/system/resolver/ns5/named.conf.in b/bin/tests/system/resolver/ns5/named.conf.in
index a98290903b..c81a3ba5de 100644
--- a/bin/tests/system/resolver/ns5/named.conf.in
+++ b/bin/tests/system/resolver/ns5/named.conf.in
@@ -22,7 +22,7 @@ options {
 	recursion yes;
 	dnssec-validation yes;
 	querylog yes;
-	prefetch 3 9;
+	prefetch 4 10;
 };
 
 server 10.53.0.7 {
diff --git a/bin/tests/system/resolver/ns6/example.net.db.in b/bin/tests/system/resolver/ns6/example.net.db.in
index fa4e96aad8..eab3267b79 100644
--- a/bin/tests/system/resolver/ns6/example.net.db.in
+++ b/bin/tests/system/resolver/ns6/example.net.db.in
@@ -16,6 +16,6 @@ mail	IN A	10.53.0.6
 fetch 10 IN TXT A short ttl
 non-zero 10 IN TXT A short ttl
 zero 0  IN TXT	A zero ttl
-$TTL 10
+$TTL 13
 ds 	IN NS	ns.ds
 ns.ds	IN A	10.53.0.6
diff --git a/bin/tests/system/resolver/ns6/fetch.tld.db b/bin/tests/system/resolver/ns6/fetch.tld.db
index 3754373ec7..b38fd51601 100644
--- a/bin/tests/system/resolver/ns6/fetch.tld.db
+++ b/bin/tests/system/resolver/ns6/fetch.tld.db
@@ -18,4 +18,4 @@ $TTL 300
 @			NS	ns.fetch.tld.
 ns.fetch.tld.		A	10.53.0.6
 
-@	10		TXT	A short ttl
+@	13		TXT	A short ttl
diff --git a/bin/tests/system/resolver/tests.sh b/bin/tests/system/resolver/tests.sh
index 7c7a8ed925..d7e0d0bd4e 100755
--- a/bin/tests/system/resolver/tests.sh
+++ b/bin/tests/system/resolver/tests.sh
@@ -451,10 +451,13 @@ status=`expr $status + $ret`
 n=`expr $n + 1`
 echo_i "check prefetch (${n})"
 ret=0
+# read prefetch value from config.
+PREFETCH=`sed -n "s/[[:space:]]*prefetch \([0-9]\).*/\1/p" ns5/named.conf`
 $DIG $DIGOPTS @10.53.0.5 fetch.tld txt > dig.out.1.${n} || ret=1
-ttl1=`awk '/"A" "short" "ttl"/ { print $2 - 3 }' dig.out.1.${n}`
+ttl1=`awk '/"A" "short" "ttl"/ { print $2 }' dig.out.1.${n}`
+interval=$((ttl1 - PREFETCH + 1))
 # sleep so we are in prefetch range
-sleep ${ttl1:-0}
+sleep ${interval:-0}
 # trigger prefetch
 $DIG $DIGOPTS @10.53.0.5 fetch.tld txt > dig.out.2.${n} || ret=1
 ttl2=`awk '/"A" "short" "ttl"/ { print $2 }' dig.out.2.${n}`
@@ -470,9 +473,10 @@ n=`expr $n + 1`
 echo_i "check prefetch of validated DS's RRSIG TTL is updated (${n})"
 ret=0
 $DIG $DIGOPTS +dnssec @10.53.0.5 ds.example.net ds > dig.out.1.${n} || ret=1
-dsttl1=`awk '$4 == "DS" && $7 == "2" { print $2 - 3 }' dig.out.1.${n}`
+dsttl1=`awk '$4 == "DS" && $7 == "2" { print $2 }' dig.out.1.${n}`
 # sleep so we are in prefetch range
-sleep ${dsttl1:-0}
+interval=$((dsttl1 - PREFETCH + 1))
+sleep ${interval:-0}
 # trigger prefetch
 $DIG $DIGOPTS @10.53.0.5 ds.example.net ds > dig.out.2.${n} || ret=1
 dsttl2=`awk '$4 == "DS" && $7 == "2" { print $2 }' dig.out.2.${n}`