diff --git a/src/libdramsys/DRAMSys/controller/Controller.cpp b/src/libdramsys/DRAMSys/controller/Controller.cpp
index b1c3941f..0c021512 100644
--- a/src/libdramsys/DRAMSys/controller/Controller.cpp
+++ b/src/libdramsys/DRAMSys/controller/Controller.cpp
@@ -387,7 +387,7 @@ void Controller::controllerMethod()
         it->evaluate();
 
     // (4) Collect all ready commands from BMs, RMs and PDMs
-    CommandTuple::Type commandTuple;
+
     // clear command buffer
     readyCommands.clear();
 
@@ -395,7 +395,7 @@ void Controller::controllerMethod()
     {
         // (4.1) Check for power-down commands (PDEA/PDEP/SREFEN or PDXA/PDXP/SREFEX)
         Rank rank = Rank(rankID);
-        commandTuple = powerDownManagers[rank]->getNextCommand();
+        auto commandTuple = powerDownManagers[rank]->getNextCommand();
         if (std::get<CommandTuple::Command>(commandTuple) != Command::NOP)
             readyCommands.emplace_back(commandTuple);
         else
@@ -426,11 +426,12 @@ void Controller::controllerMethod()
             std::get<CommandTuple::Timestamp>(it) =
                 checker->timeToSatisfyConstraints(command, *trans);
         }
-        commandTuple = cmdMux->selectCommand(readyCommands);
-        Command command = std::get<CommandTuple::Command>(commandTuple);
-        tlm_generic_payload* trans = std::get<CommandTuple::Payload>(commandTuple);
-        if (command != Command::NOP) // can happen with FIFO strict
+        auto commandTuple = cmdMux->selectCommand(readyCommands);
+        if (commandTuple.has_value()) // can happen with FIFO strict
         {
+            Command command = std::get<CommandTuple::Command>(*commandTuple);
+            tlm_generic_payload* trans = std::get<CommandTuple::Payload>(*commandTuple);
+
             Rank rank = ControllerExtension::getRank(*trans);
             Bank bank = ControllerExtension::getBank(*trans);
 
@@ -492,7 +493,7 @@ void Controller::controllerMethod()
     for (auto& it : bankMachines)
     {
         it->evaluate();
-        commandTuple = it->getNextCommand();
+        auto commandTuple = it->getNextCommand();
         Command command = std::get<CommandTuple::Command>(commandTuple);
         tlm_generic_payload* trans = std::get<CommandTuple::Payload>(commandTuple);
         if (command != Command::NOP)
@@ -505,7 +506,7 @@ void Controller::controllerMethod()
     for (auto& it : refreshManagers)
     {
         it->evaluate();
-        commandTuple = it->getNextCommand();
+        auto commandTuple = it->getNextCommand();
         Command command = std::get<CommandTuple::Command>(commandTuple);
         tlm_generic_payload* trans = std::get<CommandTuple::Payload>(commandTuple);
         if (command != Command::NOP)
@@ -522,7 +523,7 @@ void Controller::controllerMethod()
     for (auto& it : powerDownManagers)
     {
         it->evaluate();
-        commandTuple = it->getNextCommand();
+        auto commandTuple = it->getNextCommand();
         Command command = std::get<CommandTuple::Command>(commandTuple);
         tlm_generic_payload* trans = std::get<CommandTuple::Payload>(commandTuple);
         if (command != Command::NOP)
diff --git a/src/libdramsys/DRAMSys/controller/cmdmux/CmdMuxIF.h b/src/libdramsys/DRAMSys/controller/cmdmux/CmdMuxIF.h
index e7971ae9..07db4ae1 100644
--- a/src/libdramsys/DRAMSys/controller/cmdmux/CmdMuxIF.h
+++ b/src/libdramsys/DRAMSys/controller/cmdmux/CmdMuxIF.h
@@ -37,6 +37,8 @@
 
 #include "DRAMSys/controller/Command.h"
 
+#include <optional>
+
 namespace DRAMSys
 {
 
@@ -52,7 +54,7 @@ public:
     CmdMuxIF() = default;
     virtual ~CmdMuxIF() = default;
 
-    virtual CommandTuple::Type selectCommand(const ReadyCommands& readyCommands) = 0;
+    virtual std::optional<CommandTuple::Type> selectCommand(const ReadyCommands& readyCommands) = 0;
 };
 
 } // namespace DRAMSys
diff --git a/src/libdramsys/DRAMSys/controller/cmdmux/CmdMuxOldest.cpp b/src/libdramsys/DRAMSys/controller/cmdmux/CmdMuxOldest.cpp
index e1672a36..04e9713f 100644
--- a/src/libdramsys/DRAMSys/controller/cmdmux/CmdMuxOldest.cpp
+++ b/src/libdramsys/DRAMSys/controller/cmdmux/CmdMuxOldest.cpp
@@ -45,7 +45,7 @@ CmdMuxOldest::CmdMuxOldest(const MemSpec& memSpec) : memSpec(memSpec)
 {
 }
 
-CommandTuple::Type CmdMuxOldest::selectCommand(const ReadyCommands& readyCommands)
+std::optional<CommandTuple::Type> CmdMuxOldest::selectCommand(const ReadyCommands& readyCommands)
 {
     auto result = readyCommands.cend();
     uint64_t lastPayloadID = UINT64_MAX;
@@ -73,10 +73,12 @@ CommandTuple::Type CmdMuxOldest::selectCommand(const ReadyCommands& readyCommand
         }
     }
 
-    if (result != readyCommands.cend() &&
-        std::get<CommandTuple::Timestamp>(*result) == sc_time_stamp())
-        return *result;
-    return {Command::NOP, nullptr, scMaxTime};
+    assert(result != readyCommands.cend());
+
+    if (std::get<CommandTuple::Timestamp>(*result) != sc_time_stamp())
+        return std::nullopt;
+
+    return *result;
 }
 
 CmdMuxOldestRasCas::CmdMuxOldestRasCas(const MemSpec& memSpec) : memSpec(memSpec)
@@ -86,7 +88,7 @@ CmdMuxOldestRasCas::CmdMuxOldestRasCas(const MemSpec& memSpec) : memSpec(memSpec
     readyRasCasCommands.reserve(2);
 }
 
-CommandTuple::Type CmdMuxOldestRasCas::selectCommand(const ReadyCommands& readyCommands)
+std::optional<CommandTuple::Type> CmdMuxOldestRasCas::selectCommand(const ReadyCommands& readyCommands)
 {
     readyRasCommands.clear();
     readyCasCommands.clear();
@@ -180,10 +182,12 @@ CommandTuple::Type CmdMuxOldestRasCas::selectCommand(const ReadyCommands& readyC
         }
     }
 
-    if (result != readyCommands.cend() &&
-        std::get<CommandTuple::Timestamp>(*result) == sc_time_stamp())
-        return *result;
-    return {Command::NOP, nullptr, scMaxTime};
+    assert(result != readyCommands.cend());
+
+    if (std::get<CommandTuple::Timestamp>(*result) != sc_time_stamp())
+        return std::nullopt;
+
+    return *result;
 }
 
 } // namespace DRAMSys
diff --git a/src/libdramsys/DRAMSys/controller/cmdmux/CmdMuxOldest.h b/src/libdramsys/DRAMSys/controller/cmdmux/CmdMuxOldest.h
index d08e5948..802f7ae0 100644
--- a/src/libdramsys/DRAMSys/controller/cmdmux/CmdMuxOldest.h
+++ b/src/libdramsys/DRAMSys/controller/cmdmux/CmdMuxOldest.h
@@ -45,7 +45,7 @@ class CmdMuxOldest : public CmdMuxIF
 {
 public:
     explicit CmdMuxOldest(const MemSpec& memSpec);
-    CommandTuple::Type selectCommand(const ReadyCommands& readyCommands) override;
+    std::optional<CommandTuple::Type> selectCommand(const ReadyCommands& readyCommands) override;
 
 private:
     const MemSpec& memSpec;
@@ -56,7 +56,7 @@ class CmdMuxOldestRasCas : public CmdMuxIF
 {
 public:
     explicit CmdMuxOldestRasCas(const MemSpec& memSpec);
-    CommandTuple::Type selectCommand(const ReadyCommands& readyCommands) override;
+    std::optional<CommandTuple::Type> selectCommand(const ReadyCommands& readyCommands) override;
 
 private:
     const MemSpec& memSpec;
diff --git a/src/libdramsys/DRAMSys/controller/cmdmux/CmdMuxStrict.cpp b/src/libdramsys/DRAMSys/controller/cmdmux/CmdMuxStrict.cpp
index f742d8e1..ac0261b5 100644
--- a/src/libdramsys/DRAMSys/controller/cmdmux/CmdMuxStrict.cpp
+++ b/src/libdramsys/DRAMSys/controller/cmdmux/CmdMuxStrict.cpp
@@ -45,7 +45,7 @@ CmdMuxStrict::CmdMuxStrict(const MemSpec& memSpec) : memSpec(memSpec)
 {
 }
 
-CommandTuple::Type CmdMuxStrict::selectCommand(const ReadyCommands& readyCommands)
+std::optional<CommandTuple::Type> CmdMuxStrict::selectCommand(const ReadyCommands& readyCommands)
 {
     auto result = readyCommands.cend();
     uint64_t lastPayloadID = UINT64_MAX;
@@ -88,7 +88,8 @@ CommandTuple::Type CmdMuxStrict::selectCommand(const ReadyCommands& readyCommand
             nextPayloadID++;
         return *result;
     }
-    return {Command::NOP, nullptr, scMaxTime};
+
+    return std::nullopt;
 }
 
 CmdMuxStrictRasCas::CmdMuxStrictRasCas(const MemSpec& memSpec) : memSpec(memSpec)
@@ -98,7 +99,7 @@ CmdMuxStrictRasCas::CmdMuxStrictRasCas(const MemSpec& memSpec) : memSpec(memSpec
     readyRasCasCommands.reserve(2);
 }
 
-CommandTuple::Type CmdMuxStrictRasCas::selectCommand(const ReadyCommands& readyCommands)
+std::optional<CommandTuple::Type> CmdMuxStrictRasCas::selectCommand(const ReadyCommands& readyCommands)
 {
     readyRasCommands.clear();
     readyCasCommands.clear();
@@ -188,7 +189,7 @@ CommandTuple::Type CmdMuxStrictRasCas::selectCommand(const ReadyCommands& readyC
             nextPayloadID++;
         return *result;
     }
-    return {Command::NOP, nullptr, scMaxTime};
+    return std::nullopt;
 }
 
 } // namespace DRAMSys
diff --git a/src/libdramsys/DRAMSys/controller/cmdmux/CmdMuxStrict.h b/src/libdramsys/DRAMSys/controller/cmdmux/CmdMuxStrict.h
index 07c4173b..8a3531de 100644
--- a/src/libdramsys/DRAMSys/controller/cmdmux/CmdMuxStrict.h
+++ b/src/libdramsys/DRAMSys/controller/cmdmux/CmdMuxStrict.h
@@ -45,7 +45,7 @@ class CmdMuxStrict : public CmdMuxIF
 {
 public:
     explicit CmdMuxStrict(const MemSpec& memSpec);
-    CommandTuple::Type selectCommand(const ReadyCommands& readyCommands) override;
+    std::optional<CommandTuple::Type> selectCommand(const ReadyCommands& readyCommands) override;
 
 private:
     uint64_t nextPayloadID = 1;
@@ -57,7 +57,7 @@ class CmdMuxStrictRasCas : public CmdMuxIF
 {
 public:
     explicit CmdMuxStrictRasCas(const MemSpec& memSpec);
-    CommandTuple::Type selectCommand(const ReadyCommands& readyCommands) override;
+    std::optional<CommandTuple::Type> selectCommand(const ReadyCommands& readyCommands) override;
 
 private:
     uint64_t nextPayloadID = 1;