diff --git a/sys/dev/atkbdc/psm.c b/sys/dev/atkbdc/psm.c
index b3433c9ec44..5b7e54f54a2 100644
--- a/sys/dev/atkbdc/psm.c
+++ b/sys/dev/atkbdc/psm.c
@@ -293,7 +293,7 @@ static struct {
     { MOUSE_MODEL_GENERIC,
       0xc0, MOUSE_PS2_PACKETSIZE, NULL, },
 };
-#define GENERIC_MOUSE_ENTRY	7
+#define GENERIC_MOUSE_ENTRY	((sizeof(vendortype) / sizeof(*vendortype)) - 1)
 
 /* device driver declarateion */
 static device_method_t psm_methods[] = {
diff --git a/sys/isa/psm.c b/sys/isa/psm.c
index b3433c9ec44..5b7e54f54a2 100644
--- a/sys/isa/psm.c
+++ b/sys/isa/psm.c
@@ -293,7 +293,7 @@ static struct {
     { MOUSE_MODEL_GENERIC,
       0xc0, MOUSE_PS2_PACKETSIZE, NULL, },
 };
-#define GENERIC_MOUSE_ENTRY	7
+#define GENERIC_MOUSE_ENTRY	((sizeof(vendortype) / sizeof(*vendortype)) - 1)
 
 /* device driver declarateion */
 static device_method_t psm_methods[] = {