diff --git a/src/main/kotlin/ru/dbotthepony/mc/otm/capability/Ext.kt b/src/main/kotlin/ru/dbotthepony/mc/otm/capability/Ext.kt
index 49063638d..833203473 100644
--- a/src/main/kotlin/ru/dbotthepony/mc/otm/capability/Ext.kt
+++ b/src/main/kotlin/ru/dbotthepony/mc/otm/capability/Ext.kt
@@ -37,7 +37,7 @@ internal fun IEnergyStorage.receiveEnergy(amount: Decimal, simulate: Boolean): D
 	if (this is IMatteryEnergyStorage)
 		return receiveEnergyChecked(amount, simulate)
 
-	if (!amount.isPositive)
+	if (amount.isNegative)
 		throw IllegalArgumentException("Negative energy: $amount")
 
 	if (!canReceive())
@@ -56,7 +56,7 @@ internal fun IEnergyStorage.extractEnergy(amount: Decimal, simulate: Boolean): D
 	if (this is IMatteryEnergyStorage)
 		return extractEnergyChecked(amount, simulate)
 
-	if (!amount.isPositive)
+	if (amount.isNegative)
 		throw IllegalArgumentException("Negative energy: $amount")
 
 	if (!canExtract())