diff --git a/sys/alpha/alpha/vm_machdep.c b/sys/alpha/alpha/vm_machdep.c
index 75bfef5b6fc..247f1b624ac 100644
--- a/sys/alpha/alpha/vm_machdep.c
+++ b/sys/alpha/alpha/vm_machdep.c
@@ -76,6 +76,7 @@
 #include <sys/vmmeter.h>
 #include <sys/kernel.h>
 #include <sys/sysctl.h>
+#include <sys/unistd.h>
 
 #include <machine/clock.h>
 #include <machine/cpu.h>
diff --git a/sys/powerpc/aim/vm_machdep.c b/sys/powerpc/aim/vm_machdep.c
index 75bfef5b6fc..247f1b624ac 100644
--- a/sys/powerpc/aim/vm_machdep.c
+++ b/sys/powerpc/aim/vm_machdep.c
@@ -76,6 +76,7 @@
 #include <sys/vmmeter.h>
 #include <sys/kernel.h>
 #include <sys/sysctl.h>
+#include <sys/unistd.h>
 
 #include <machine/clock.h>
 #include <machine/cpu.h>
diff --git a/sys/powerpc/powerpc/vm_machdep.c b/sys/powerpc/powerpc/vm_machdep.c
index 75bfef5b6fc..247f1b624ac 100644
--- a/sys/powerpc/powerpc/vm_machdep.c
+++ b/sys/powerpc/powerpc/vm_machdep.c
@@ -76,6 +76,7 @@
 #include <sys/vmmeter.h>
 #include <sys/kernel.h>
 #include <sys/sysctl.h>
+#include <sys/unistd.h>
 
 #include <machine/clock.h>
 #include <machine/cpu.h>