diff --git a/bin/ps/keyword.c b/bin/ps/keyword.c
index a3d00662ed60..1749c2846917 100644
--- a/bin/ps/keyword.c
+++ b/bin/ps/keyword.c
@@ -42,6 +42,7 @@ static const char rcsid[] =
 
 #include <sys/param.h>
 #include <sys/time.h>
+#include <sys/lock.h>
 #include <sys/resource.h>
 #include <sys/proc.h>
 #include <sys/sysctl.h>
diff --git a/bin/ps/print.c b/bin/ps/print.c
index f73c3f06d09b..8762700ac6a2 100644
--- a/bin/ps/print.c
+++ b/bin/ps/print.c
@@ -40,6 +40,7 @@ static const char rcsid[] =
 #endif /* not lint */
 
 #include <sys/param.h>
+#include <sys/lock.h>
 #include <sys/time.h>
 #include <sys/resource.h>
 #include <sys/proc.h>
diff --git a/bin/ps/ps.c b/bin/ps/ps.c
index 628ca377c7d1..7613a57e40da 100644
--- a/bin/ps/ps.c
+++ b/bin/ps/ps.c
@@ -46,6 +46,7 @@ static const char rcsid[] =
 #endif /* not lint */
 
 #include <sys/param.h>
+#include <sys/lock.h>
 #include <sys/user.h>
 #include <sys/time.h>
 #include <sys/resource.h>