diff --git a/tests/simulator-ng.pl b/tests/simulator-ng.pl
index 2eab8515e..0c17aa910 100755
--- a/tests/simulator-ng.pl
+++ b/tests/simulator-ng.pl
@@ -46,7 +46,7 @@ GetOptions(
 
 ($IP || $IPV6) or die("at least one of --local-ip or --local-ipv6 must be given");
 
-$SIG{ALRM} = sub { print "alarm!\n"; };
+local $SIG{ALRM} = sub { print "alarm!\n"; };
 setrlimit(RLIMIT_NOFILE, 8000, 8000);
 
 $PROTOS and $PROTOS = [split(/\s*[,;:]+\s*/, $PROTOS)];
diff --git a/tests/simulator-udp.pl b/tests/simulator-udp.pl
index 035cbd1f6..5ae170a8a 100755
--- a/tests/simulator-udp.pl
+++ b/tests/simulator-udp.pl
@@ -23,7 +23,7 @@ GetOptions(
 
 ($IP || $IPV6) or die("at least one of --local-ip or --local-ipv6 must be given");
 
-$SIG{ALRM} = sub { print "alarm!\n"; };
+local $SIG{ALRM} = sub { print "alarm!\n"; };
 setrlimit(RLIMIT_NOFILE, 8000, 8000);
 
 my @chrs = ('a' .. 'z', 'A' .. 'Z', '0' .. '9');