diff --git a/Source/Core/Core/HW/SI/SI.cpp b/Source/Core/Core/HW/SI/SI.cpp
index ff349c64bf..7b17a213c1 100644
--- a/Source/Core/Core/HW/SI/SI.cpp
+++ b/Source/Core/Core/HW/SI/SI.cpp
@@ -240,7 +240,6 @@ static void SetNoResponse(u32 channel)
     s_status_reg.NOREP3 = 1;
     break;
   }
-  s_com_csr.COMERR = 1;
 }
 
 static void ChangeDeviceCallback(u64 user_data, s64 cycles_late)
@@ -286,7 +285,7 @@ static void GenerateSIInterrupt(SIInterruptType type)
 constexpr u32 SI_XFER_LENGTH_MASK = 0x7f;
 
 // Translate [0,1,2,...,126,127] to [128,1,2,...,126,127]
-constexpr u32 ConvertSILengthField(u32 field)
+constexpr s32 ConvertSILengthField(u32 field)
 {
   return ((field - 1) & SI_XFER_LENGTH_MASK) + 1;
 }
@@ -295,19 +294,19 @@ static void RunSIBuffer(u64 user_data, s64 cycles_late)
 {
   if (s_com_csr.TSTART)
   {
-    const u32 request_length = ConvertSILengthField(s_com_csr.OUTLNGTH);
-    const u32 expected_response_length = ConvertSILengthField(s_com_csr.INLNGTH);
+    const s32 request_length = ConvertSILengthField(s_com_csr.OUTLNGTH);
+    const s32 expected_response_length = ConvertSILengthField(s_com_csr.INLNGTH);
     const std::vector<u8> request_copy(s_si_buffer.data(), s_si_buffer.data() + request_length);
 
     const std::unique_ptr<ISIDevice>& device = s_channel[s_com_csr.CHANNEL].device;
-    const u32 actual_response_length = device->RunBuffer(s_si_buffer.data(), request_length);
+    const s32 actual_response_length = device->RunBuffer(s_si_buffer.data(), request_length);
 
     DEBUG_LOG_FMT(SERIALINTERFACE,
                   "RunSIBuffer  chan: {}  request_length: {}  expected_response_length: {}  "
                   "actual_response_length: {}",
                   s_com_csr.CHANNEL, request_length, expected_response_length,
                   actual_response_length);
-    if (expected_response_length != actual_response_length)
+    if (actual_response_length > 0 && expected_response_length != actual_response_length)
     {
       std::ostringstream ss;
       for (u8 b : request_copy)
@@ -331,6 +330,9 @@ static void RunSIBuffer(u64 user_data, s64 cycles_late)
     if (actual_response_length != 0)
     {
       s_com_csr.TSTART = 0;
+      s_com_csr.COMERR = actual_response_length < 0;
+      if (actual_response_length < 0)
+        SetNoResponse(s_com_csr.CHANNEL);
       GenerateSIInterrupt(INT_TCINT);
     }
     else
@@ -501,8 +503,6 @@ void RegisterMMIO(MMIO::Mapping* mmio, u32 base)
                    s_com_csr.RDSTINTMSK = tmp_com_csr.RDSTINTMSK;
                    s_com_csr.TCINTMSK = tmp_com_csr.TCINTMSK;
 
-                   s_com_csr.COMERR = 0;
-
                    if (tmp_com_csr.RDSTINT)
                      s_com_csr.RDSTINT = 0;
                    if (tmp_com_csr.TCINT)
diff --git a/Source/Core/Core/HW/SI/SI_DeviceGBA.cpp b/Source/Core/Core/HW/SI/SI_DeviceGBA.cpp
index 9268ca9127..36561a6ffb 100644
--- a/Source/Core/Core/HW/SI/SI_DeviceGBA.cpp
+++ b/Source/Core/Core/HW/SI/SI_DeviceGBA.cpp
@@ -332,10 +332,9 @@ int CSIDevice_GBA::RunBuffer(u8* buffer, int request_length)
     }
     else
     {
-      u32 reply = Common::swap32(SI_ERROR_NO_RESPONSE);
-      std::memcpy(buffer, &reply, sizeof(reply));
-      return sizeof(reply);
+      return -1;
     }
+
     m_last_cmd = buffer[0];
     m_timestamp_sent = CoreTiming::GetTicks();
     m_next_action = NextAction::WaitTransferTime;
@@ -371,11 +370,7 @@ int CSIDevice_GBA::RunBuffer(u8* buffer, int request_length)
 
     m_next_action = NextAction::SendCommand;
     if (num_data_received == 0)
-    {
-      u32 reply = Common::swap32(SI_ERROR_NO_RESPONSE);
-      std::memcpy(buffer, &reply, sizeof(reply));
-      return sizeof(reply);
-    }
+      return -1;
 #ifdef _DEBUG
     const Common::Log::LOG_LEVELS log_level =
         (m_last_cmd == CMD_STATUS || m_last_cmd == CMD_RESET) ? Common::Log::LERROR :
diff --git a/Source/Core/Core/HW/SI/SI_DeviceGCController.cpp b/Source/Core/Core/HW/SI/SI_DeviceGCController.cpp
index 4cf332347b..3393a996c4 100644
--- a/Source/Core/Core/HW/SI/SI_DeviceGCController.cpp
+++ b/Source/Core/Core/HW/SI/SI_DeviceGCController.cpp
@@ -43,11 +43,7 @@ int CSIDevice_GCController::RunBuffer(u8* buffer, int request_length)
 
   GCPadStatus pad_status = GetPadStatus();
   if (!pad_status.isConnected)
-  {
-    u32 reply = Common::swap32(SI_ERROR_NO_RESPONSE);
-    std::memcpy(buffer, &reply, sizeof(reply));
-    return sizeof(reply);
-  }
+    return -1;
 
   // Read the command
   EBufferCommands command = static_cast<EBufferCommands>(buffer[0]);
diff --git a/Source/Core/Core/HW/SI/SI_DeviceNull.cpp b/Source/Core/Core/HW/SI/SI_DeviceNull.cpp
index f4ed00e7ae..6a2b16f2a0 100644
--- a/Source/Core/Core/HW/SI/SI_DeviceNull.cpp
+++ b/Source/Core/Core/HW/SI/SI_DeviceNull.cpp
@@ -16,9 +16,7 @@ CSIDevice_Null::CSIDevice_Null(SIDevices device, int device_number)
 
 int CSIDevice_Null::RunBuffer(u8* buffer, int request_length)
 {
-  u32 reply = Common::swap32(SI_ERROR_NO_RESPONSE);
-  std::memcpy(buffer, &reply, sizeof(reply));
-  return sizeof(reply);
+  return -1;
 }
 
 bool CSIDevice_Null::GetData(u32& hi, u32& low)