diff --git a/hal/gonk/GonkHal.cpp b/hal/gonk/GonkHal.cpp
index c2abe7a2235..4c98315b003 100644
--- a/hal/gonk/GonkHal.cpp
+++ b/hal/gonk/GonkHal.cpp
@@ -256,6 +256,10 @@ DisableBatteryNotifications()
 void
 GetCurrentBatteryInformation(hal::BatteryInformation *aBatteryInfo)
 {
+  static const int BATTERY_NOT_CHARGING = 0;
+  static const int BATTERY_CHARGING_USB = 1;
+  static const int BATTERY_CHARGING_AC  = 2;
+
   FILE *capacityFile = fopen("/sys/class/power_supply/battery/capacity", "r");
   double capacity = dom::battery::kDefaultLevel * 100;
   if (capacityFile) {
@@ -270,8 +274,17 @@ GetCurrentBatteryInformation(hal::BatteryInformation *aBatteryInfo)
     fclose(chargingFile);
   }
 
+  #ifdef DEBUG
+  if (chargingSrc != BATTERY_NOT_CHARGING &&
+      chargingSrc != BATTERY_CHARGING_USB &&
+      chargingSrc != BATTERY_CHARGING_AC) {
+    HAL_LOG(("charging_source contained unknown value: %d", chargingSrc));
+  }
+  #endif
+
   aBatteryInfo->level() = capacity / 100;
-  aBatteryInfo->charging() = chargingSrc == 1;
+  aBatteryInfo->charging() = (chargingSrc == BATTERY_CHARGING_USB ||
+                              chargingSrc == BATTERY_CHARGING_AC);
   aBatteryInfo->remainingTime() = dom::battery::kUnknownRemainingTime;
 }