diff --git a/t/lib/CliRunners.pm b/t/lib/CliRunners.pm
index e693eeb7..7ae936c0 100644
--- a/t/lib/CliRunners.pm
+++ b/t/lib/CliRunners.pm
@@ -27,6 +27,8 @@ sub evalSucceeds {
     $jobset->discard_changes;  # refresh from DB
     if ($res) {
         chomp $stdout; chomp $stderr;
+        utf8::decode($stdout) or die "Invalid unicode in stdout.";
+        utf8::decode($stderr) or die "Invalid unicode in stderr.";
         print STDERR "Evaluation unexpectedly failed for jobset ".$jobset->project->name.":".$jobset->name.": \n".$jobset->errormsg."\n" if $jobset->errormsg;
         print STDERR "STDOUT: $stdout\n" if $stdout ne "";
         print STDERR "STDERR: $stderr\n" if $stderr ne "";
@@ -40,6 +42,8 @@ sub evalFails {
     $jobset->discard_changes;  # refresh from DB
     if (!$res) {
         chomp $stdout; chomp $stderr;
+        utf8::decode($stdout) or die "Invalid unicode in stdout.";
+        utf8::decode($stderr) or die "Invalid unicode in stderr.";
         print STDERR "Evaluation unexpectedly succeeded for jobset ".$jobset->project->name.":".$jobset->name.": \n".$jobset->errormsg."\n" if $jobset->errormsg;
         print STDERR "STDOUT: $stdout\n" if $stdout ne "";
         print STDERR "STDERR: $stderr\n" if $stderr ne "";
@@ -51,6 +55,8 @@ sub runBuild {
     my ($build) = @_;
     my ($res, $stdout, $stderr) = captureStdoutStderr(60, ("hydra-queue-runner", "-vvvv", "--build-one", $build->id));
     if ($res) {
+        utf8::decode($stdout) or die "Invalid unicode in stdout.";
+        utf8::decode($stderr) or die "Invalid unicode in stderr.";
         print STDERR "Queue runner stdout: $stdout\n" if $stdout ne "";
         print STDERR "Queue runner stderr: $stderr\n" if $stderr ne "";
     }
@@ -60,6 +66,8 @@ sub runBuild {
 sub sendNotifications() {
     my ($res, $stdout, $stderr) = captureStdoutStderr(60, ("hydra-notify", "--queued-only"));
     if ($res) {
+        utf8::decode($stdout) or die "Invalid unicode in stdout.";
+        utf8::decode($stderr) or die "Invalid unicode in stderr.";
         print STDERR "hydra notify stdout: $stdout\n" if $stdout ne "";
         print STDERR "hydra notify stderr: $stderr\n" if $stderr ne "";
     }