diff --git a/passes/cmds/linux_perf.cc b/passes/cmds/linux_perf.cc
index f57a887fb..bb1339dd8 100644
--- a/passes/cmds/linux_perf.cc
+++ b/passes/cmds/linux_perf.cc
@@ -23,6 +23,7 @@
 
 #include <fcntl.h>
 #include <stdlib.h>
+#include <unistd.h>
 
 USING_YOSYS_NAMESPACE
 PRIVATE_NAMESPACE_BEGIN