diff --git a/bin/tests/system/masterformat/clean.sh b/bin/tests/system/masterformat/clean.sh
index 80289e9267..82502fc430 100755
--- a/bin/tests/system/masterformat/clean.sh
+++ b/bin/tests/system/masterformat/clean.sh
@@ -26,7 +26,7 @@ rm -f ./ns2/formerly-text.db
 rm -f ./ns2/db-*
 rm -f ./ns2/large.bk
 rm -f ./ns3/example.db.map ./ns3/dynamic.db.map
-rm -f ./baseline.txt ./text.1 ./text.2 ./raw.1 ./raw.2 ./map.1 ./map.2 ./map.5 ./text.5 ./badmap
+rm -f ./baseline.txt ./text.* ./raw.* ./map.* ./badmap
 rm -f ./ns1/Ksigned.* ./ns1/dsset-signed. ./ns1/signed.db.signed
 rm -f ./rndc.out
 rm -f ./ns*/named.lock
diff --git a/bin/tests/system/masterformat/tests.sh b/bin/tests/system/masterformat/tests.sh
index 0f569fd059..364a0d266d 100755
--- a/bin/tests/system/masterformat/tests.sh
+++ b/bin/tests/system/masterformat/tests.sh
@@ -331,5 +331,25 @@ n=$((n+1))
 [ $ret -eq 0 ] || echo_i "failed"
 status=$((status+ret))
 
+# The following test is disabled by default because it is very slow.
+# It fails on Windows, because a single read() call (specifically
+# the one in isc_file_mmap()) cannot process more than INT_MAX (2^31)
+# bytes of data.
+if [ -n "${TEST_LARGE_MAP}" ]; then
+    echo_i "checking map file size > 2GB can be loaded ($n)"
+    ret=0
+    $PERL ../../startperf/mkzonefile.pl test 9000000 > text.$n
+    # convert to map
+    $CHECKZONE -D -f text -F map -o map.$n test text.$n > /dev/null || ret=1
+    # check map file size is over 2GB to ensure the test is valid
+    size=$(ls -l map.$n | awk '{print $5}')
+    [ "$size" -gt 2147483648 ] || ret=1
+    # convert back to text
+    $CHECKZONE -f map test map.$n > /dev/null || ret=1
+    n=$((n+1))
+    [ $ret -eq 0 ] || echo_i "failed"
+    status=$((status+ret))
+fi
+
 echo_i "exit status: $status"
 [ $status -eq 0 ] || exit 1