diff --git a/src/bin/system/machine/sensors.bogox b/src/bin/system/machine/sensors.bogox
index eff3a98..77de13f 100644
--- a/src/bin/system/machine/sensors.bogox
+++ b/src/bin/system/machine/sensors.bogox
@@ -277,7 +277,7 @@ _power_battery_count_get(power_t *power)
           }
      }
 #elif defined(__FreeBSD__) || defined(__DragonFly__)
-   size_t len;
+   size_t len = sizeof(power->battery_count);
 
    if ((sysctlbyname("hw.acpi.battery.units", &power->battery_count, &len, NULL, 0))  < 0)
      power->battery_count = 0;