diff --git a/help/CommandLine.html b/help/CommandLine.html
index abd3fad5..67cee417 100644
--- a/help/CommandLine.html
+++ b/help/CommandLine.html
@@ -226,5 +226,11 @@
 		<br><br>
 		-screenshot-and-exit<br>
 		For testing. Use in combination with -load-state.<br><br>
+		-hdc-firmware-v1<br>
+		Force all attached hard disk controllers to use the old v1 firmware (as per pre-AppleWin 1.30.17).
+		<ul>
+			<li>NB. Switch likely to be removed after a few releases.</li>
+		</ul>
+		<br><br>
 	</body>
 </html>
diff --git a/source/CmdLine.cpp b/source/CmdLine.cpp
index e1a399cc..3ad9d64b 100644
--- a/source/CmdLine.cpp
+++ b/source/CmdLine.cpp
@@ -253,10 +253,14 @@ bool ProcessCmdLine(LPSTR lpCmdLine)
 			lpNextArg = GetNextArg(lpNextArg);
 			g_cmdLine.uHarddiskNumBlocks = atoi(lpCmdLine);
 			if (g_cmdLine.uHarddiskNumBlocks > kHarddiskMaxNumBlocks)
+			{
 				g_cmdLine.uHarddiskNumBlocks = kHarddiskMaxNumBlocks;
+			}
 			else
+			{
 				if (g_cmdLine.uHarddiskNumBlocks < 0)
 					g_cmdLine.uHarddiskNumBlocks = 0;
+			}
 		}
 		else if (strcmp(lpCmdLine, "-load-state") == 0)
 		{
@@ -627,10 +631,14 @@ bool ProcessCmdLine(LPSTR lpCmdLine)
 		{
 			g_cmdLine.supportExtraMBCardTypes = true;
 		}
-		else if (strcmp(lpCmdLine, "-no-disk2-stepper-defer") == 0)	// a debug switch (likely to be removed in a future version)
+		else if (strcmp(lpCmdLine, "-no-disk2-stepper-defer") == 0)	// a debug switch added at 1.30.11 / GH#1110 (likely to be removed in a future version)
 		{
 			g_cmdLine.noDisk2StepperDefer = true;
 		}
+		else if (strcmp(lpCmdLine, "-hdc-firmware-v1") == 0)	// a debug switch added at 1.30.18 / GH#1277 (likely to be removed in a future version)
+		{
+			g_cmdLine.useHdcFirmwareV1 = true;
+		}
 		else	// unsupported
 		{
 			LogFileOutput("Unsupported arg: %s\n", lpCmdLine);
diff --git a/source/CmdLine.h b/source/CmdLine.h
index a5f45651..b8ac0a26 100644
--- a/source/CmdLine.h
+++ b/source/CmdLine.h
@@ -34,6 +34,7 @@ struct CmdLine
 		enableDumpToRealPrinter = false;
 		supportExtraMBCardTypes = false;
 		noDisk2StepperDefer = false;
+		useHdcFirmwareV1 = false;
 		szSnapshotName = NULL;
 		szScreenshotFilename = NULL;
 		uHarddiskNumBlocks = 0;
@@ -78,6 +79,7 @@ struct CmdLine
 	bool enableDumpToRealPrinter;
 	bool supportExtraMBCardTypes;
 	bool noDisk2StepperDefer;	// debug
+	bool useHdcFirmwareV1;	// debug
 	SS_CARDTYPE slotInsert[NUM_SLOTS];
 	SlotInfo slotInfo[NUM_SLOTS];
 	LPCSTR szImageName_drive[NUM_SLOTS][NUM_DRIVES];
diff --git a/source/Harddisk.cpp b/source/Harddisk.cpp
index 0a0ddc57..f26a0e2b 100644
--- a/source/Harddisk.cpp
+++ b/source/Harddisk.cpp
@@ -131,7 +131,7 @@ Overview
 
 
 HarddiskInterfaceCard::HarddiskInterfaceCard(UINT slot) :
-	Card(CT_GenericHDD, slot)
+	Card(CT_GenericHDD, slot), m_userNumBlocks(0), m_useHdcFirmwareV1(false)
 {
 	if (m_slot != SLOT5 && m_slot != SLOT7)	// fixme
 		ThrowErrorInvalidSlot();
@@ -166,7 +166,8 @@ void HarddiskInterfaceCard::InitializeIO(LPBYTE pCxRomPeripheral)
 {
 	const DWORD HARDDISK_FW_SIZE = APPLE_SLOT_SIZE;
 
-	BYTE* pData = GetFrame().GetResource(IDR_HDDRVR_V2_FW, "FIRMWARE", HARDDISK_FW_SIZE);
+	const WORD id = m_useHdcFirmwareV1 ? IDR_HDDRVR_FW : IDR_HDDRVR_V2_FW;
+	BYTE* pData = GetFrame().GetResource(id, "FIRMWARE", HARDDISK_FW_SIZE);
 	if (pData == NULL)
 		return;
 
diff --git a/source/Harddisk.h b/source/Harddisk.h
index 048f0051..4733c5c0 100644
--- a/source/Harddisk.h
+++ b/source/Harddisk.h
@@ -101,6 +101,7 @@ public:
 	bool IsDriveUnplugged(const int iDrive);
 	void LoadLastDiskImage(const int iDrive);
 	void SetUserNumBlocks(UINT numBlocks) { m_userNumBlocks = numBlocks; }
+	void UseHdcFirmwareV1(void) { m_useHdcFirmwareV1 = true; }
 
 	void GetLightStatus(Disk_Status_e* pDisk1Status);
 	bool ImageSwap(void);
@@ -130,6 +131,7 @@ private:
 	BYTE m_command;
 	UINT64 m_notBusyCycle;
 	UINT m_userNumBlocks;
+	bool m_useHdcFirmwareV1;
 
 	bool m_saveDiskImage;	// Save the DiskImage name to Registry
 
diff --git a/source/Windows/AppleWin.cpp b/source/Windows/AppleWin.cpp
index ba902b86..82a796a3 100644
--- a/source/Windows/AppleWin.cpp
+++ b/source/Windows/AppleWin.cpp
@@ -803,7 +803,11 @@ static void RepeatInitialization(void)
 			if (GetCardMgr().QuerySlot(i) == CT_Disk2 && g_cmdLine.slotInfo[i].isDiskII13)
 				dynamic_cast<Disk2InterfaceCard&>(GetCardMgr().GetRef(i)).SetFirmware13Sector();
 			if (GetCardMgr().QuerySlot(i) == CT_GenericHDD)
+			{
 				dynamic_cast<HarddiskInterfaceCard&>(GetCardMgr().GetRef(i)).SetUserNumBlocks(g_cmdLine.uHarddiskNumBlocks);
+				if (g_cmdLine.useHdcFirmwareV1)
+					dynamic_cast<HarddiskInterfaceCard&>(GetCardMgr().GetRef(i)).UseHdcFirmwareV1();
+			}
 		}
 
 		// Create window after inserting/removing VidHD card (as it affects width & height)