diff --git a/src/hydra-queue-runner/queue-monitor.cc b/src/hydra-queue-runner/queue-monitor.cc
index cce60da9..d6d87e71 100644
--- a/src/hydra-queue-runner/queue-monitor.cc
+++ b/src/hydra-queue-runner/queue-monitor.cc
@@ -5,6 +5,7 @@
 #include <nix/util/thread-pool.hh>
 
 #include <cstring>
+#include <signal.h>
 
 using namespace nix;