diff --git a/src/bsdapm.cc b/src/bsdapm.cc
index 830ed32d..89fb60fb 100644
--- a/src/bsdapm.cc
+++ b/src/bsdapm.cc
@@ -33,6 +33,7 @@
 #include <fcntl.h>
 #include <sys/ioctl.h>
 #include <machine/apm_bios.h>
+#include <unistd.h>
 
 #define	APMDEV		"/dev/apm"
 #define	APM_UNKNOWN	255