diff --git a/DRAMSys/simulator/src/controller/core/scheduling/checker/PowerDownChecker.cpp b/DRAMSys/simulator/src/controller/core/scheduling/checker/PowerDownChecker.cpp
index 5d95cad2..c9a8a988 100644
--- a/DRAMSys/simulator/src/controller/core/scheduling/checker/PowerDownChecker.cpp
+++ b/DRAMSys/simulator/src/controller/core/scheduling/checker/PowerDownChecker.cpp
@@ -80,14 +80,17 @@ void PowerDownChecker::delayToSatisfyConstraints(ScheduledCommand &command) cons
 
 		// Get the last scheduled command on this bank
 		ScheduledCommand lastSchedCmdOnBank = state.getLastScheduledCommand(bank);
-		// Get the start time for the last scheduled command on this bank
-		sc_time lastSchedCmdOnBankStart = lastSchedCmdOnBank.getStart();
-		// Get the last command on this bank itself
-		Command lastCmdBank = lastSchedCmdOnBank.getCommand();
 
-		timeConstraint = getTimeConstraintToEnterPowerDown(lastCmdBank, pdnCmd);
+        if (lastSchedCmdOnBank.isValidCommand()) {
+		    // Get the start time for the last scheduled command on this bank
+		    sc_time lastSchedCmdOnBankStart = lastSchedCmdOnBank.getStart();
+		    // Get the last command on this bank itself
+		    Command lastCmdBank = lastSchedCmdOnBank.getCommand();
 
-		command.establishMinDistanceFromStart(lastSchedCmdOnBankStart, timeConstraint);
+		    timeConstraint = getTimeConstraintToEnterPowerDown(lastCmdBank, pdnCmd);
+
+		    command.establishMinDistanceFromStart(lastSchedCmdOnBankStart, timeConstraint);
+        }
 
 	} else if (pdnCmd == Command::PDNAX) {
 		// Leaving Active Power Down