diff --git a/src/script/hydra-queue-runner b/src/script/hydra-queue-runner
index 5937656a..9443c8b2 100755
--- a/src/script/hydra-queue-runner
+++ b/src/script/hydra-queue-runner
@@ -48,6 +48,7 @@ sub unlockDeadBuilds {
 # depends; or undef if no such build exists.
 sub findBuildDependencyInQueue {
     my ($buildsByDrv, $build) = @_;
+    return undef unless isValidPath($build->drvpath);
     my @deps = grep { /\.drv$/ && $_ ne $build->drvpath } computeFSClosure(0, 0, $build->drvpath);
     return unless scalar @deps > 0;
     foreach my $d (@deps) {