diff --git a/bin/tests/system/resolver/ns4/tld1.db b/bin/tests/system/resolver/ns4/tld1.db
index 6b90e1b1ba..f9a9463440 100644
--- a/bin/tests/system/resolver/ns4/tld1.db
+++ b/bin/tests/system/resolver/ns4/tld1.db
@@ -20,7 +20,7 @@ ns			A	10.53.0.4
 $TTL 5
 to-be-removed 		NS	ns.to-be-removed
 ns.to-be-removed	A	10.53.0.6
-fetch	10		TXT	A short ttl
+fetch	13		TXT	A short ttl
 no-edns-version.tld.	NS	ns.no-edns-version.tld.
 ns.no-edns-version.tld.	A	10.53.0.6
 edns-version.tld.	NS	ns.edns-version.tld.
diff --git a/bin/tests/system/resolver/ns4/tld2.db b/bin/tests/system/resolver/ns4/tld2.db
index 22e1d4ed79..24ed348d89 100644
--- a/bin/tests/system/resolver/ns4/tld2.db
+++ b/bin/tests/system/resolver/ns4/tld2.db
@@ -17,7 +17,7 @@ $TTL 300
 				)
 @			NS	ns.tld.
 ns			A	10.53.0.4
-fetch  10              TXT     A short ttl
+fetch  13              TXT     A short ttl
 fetchall  10              TXT     A short ttl
 fetchall  10              A     1.2.3.4
 fetchall  10              AAAA    ::1
diff --git a/bin/tests/system/resolver/ns5/named.conf.in b/bin/tests/system/resolver/ns5/named.conf.in
index 07205c9938..f6f96f3fc4 100644
--- a/bin/tests/system/resolver/ns5/named.conf.in
+++ b/bin/tests/system/resolver/ns5/named.conf.in
@@ -21,6 +21,7 @@ options {
 	listen-on-v6 { none; };
 	recursion yes;
 	querylog yes;
+	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/tests.sh b/bin/tests/system/resolver/tests.sh
index 02f713dce4..4001136683 100755
--- a/bin/tests/system/resolver/tests.sh
+++ b/bin/tests/system/resolver/tests.sh
@@ -443,10 +443,13 @@ 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 $2 - 2 }' dig.out.1.${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}`
@@ -462,9 +465,10 @@ 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 == "1" { print $2 - 2 }' dig.out.1.${n}`
+dsttl1=`awk '$4 == "DS" && $7 == "1" { 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 == "1" { print $2 }' dig.out.2.${n}`