diff --git a/biofuel-manager.lua b/biofuel-manager.lua
index bc3211d..ff08bfd 100644
--- a/biofuel-manager.lua
+++ b/biofuel-manager.lua
@@ -124,7 +124,11 @@ function getOrders ()
     local orders = {}
     -- Oil
     local oil_amt = table.remove(peripheral.call(OIL_TANK, "tanks"))
-    if oil_amt == nil then oil_amt = 0 end
+    if oil_amt == nil then
+        oil_amt = 0
+    else
+        oil_amt = oil_amt.amount
+    end
     local oil_needed = OIL_SETPOINT - oil_amt
     if oil_needed > 0 then orders.oil = oil_needed end
     -- Biomass
@@ -136,7 +140,11 @@ function getOrders ()
     -- Biofuel
     -- TODO use up excess material?
     local biofuel_amt = table.remove(peripheral.call(FUEL_TANK, "tanks"))
-    if biofuel_amt == nil then biofuel_amt = 0 end
+    if biofuel_amt == nil then
+        biofuel_amt = 0
+    else
+        biofuel_amt = biofuel_amt.amount
+    end
     local biofuel_needed = BIOFUEL_SETPOINT - biofuel_amt
     if biofuel_needed > 0 then orders.biofuel = biofuel_needed end
     return orders