diff --git a/Downstream/Inc/downstream_spi.h b/Downstream/Inc/downstream_spi.h
index 8a2b028..1a95b69 100644
--- a/Downstream/Inc/downstream_spi.h
+++ b/Downstream/Inc/downstream_spi.h
@@ -26,9 +26,8 @@
 
 #define DOWNSTREAM_SPI_FREAKOUT									\
 	do {														\
-		LED_Fault_SetBlinkRate(LED_FAST_BLINK_RATE);			\
-		/*Downstream_PacketProcessor_SetErrorState();*/				\
-		/*DownstreamInterfaceState = DOWNSTREAM_INTERFACE_ERROR;*/	\
+		Downstream_PacketProcessor_FreakOut();					\
+		DownstreamInterfaceState = DOWNSTREAM_INTERFACE_ERROR;	\
 		while (1);												\
 	} while (0);
 
diff --git a/Downstream/Inc/downstream_statemachine.h b/Downstream/Inc/downstream_statemachine.h
index 785f055..97fc1a5 100644
--- a/Downstream/Inc/downstream_statemachine.h
+++ b/Downstream/Inc/downstream_statemachine.h
@@ -14,6 +14,7 @@
 
 
 #include "usbh_def.h"
+#include "usb_host.h"
 #include "downstream_spi.h"
 
 
@@ -30,6 +31,7 @@ typedef enum
 
 #define DOWNSTREAM_STATEMACHINE_FREAKOUT				\
 	do {												\
+		USB_Host_Disconnect();							\
 		LED_Fault_SetBlinkRate(LED_FAST_BLINK_RATE);	\
 		DownstreamState = STATE_ERROR;					\
 		while (1);										\
diff --git a/Downstream/Inc/usb_host.h b/Downstream/Inc/usb_host.h
index a59c43b..d324d0c 100644
--- a/Downstream/Inc/usb_host.h
+++ b/Downstream/Inc/usb_host.h
@@ -54,6 +54,7 @@ typedef enum {
 
 void USB_Host_Init(void);
 void USB_Host_Process(void);
+void USB_Host_Disconnect(void);
 
 
 #ifdef __cplusplus
diff --git a/Downstream/Middlewares/ST/STM32_USB_Host_Library/Core/Inc/usbh_core.h b/Downstream/Middlewares/ST/STM32_USB_Host_Library/Core/Inc/usbh_core.h
index 25a3dcb..92d159c 100644
--- a/Downstream/Middlewares/ST/STM32_USB_Host_Library/Core/Inc/usbh_core.h
+++ b/Downstream/Middlewares/ST/STM32_USB_Host_Library/Core/Inc/usbh_core.h
@@ -67,7 +67,7 @@
 #define HOST_USER_CONNECTION                    4
 #define HOST_USER_DISCONNECTION                 5
 #define HOST_USER_UNRECOVERED_ERROR             6
-
+#define HOST_USER_CLASS_FAILED					7
 
 /**
   * @}
diff --git a/Downstream/Middlewares/ST/STM32_USB_Host_Library/Core/Src/usbh_core.c b/Downstream/Middlewares/ST/STM32_USB_Host_Library/Core/Src/usbh_core.c
index e4d3553..d049a4f 100644
--- a/Downstream/Middlewares/ST/STM32_USB_Host_Library/Core/Src/usbh_core.c
+++ b/Downstream/Middlewares/ST/STM32_USB_Host_Library/Core/Src/usbh_core.c
@@ -534,6 +534,7 @@ USBH_StatusTypeDef  USBH_Process(USBH_HandleTypeDef *phost)
         }
         else
         {
+          phost->pUser(phost, HOST_USER_CLASS_FAILED);
           phost->gState  = HOST_ABORT_STATE;
           USBH_UsrLog ("Device not supporting %s class.", phost->pActiveClass->Name);
         }
diff --git a/Downstream/Src/downstream_statemachine.c b/Downstream/Src/downstream_statemachine.c
index 03f0b79..ee3d281 100644
--- a/Downstream/Src/downstream_statemachine.c
+++ b/Downstream/Src/downstream_statemachine.c
@@ -89,14 +89,8 @@ void Downstream_PacketProcessor(DownstreamPacketTypeDef* receivedPacket)
 }
 
 
-//Used by downstream_spi freakout macro, indicates we should stop everything.
-void Downstream_PacketProcessor_SetErrorState(void)
-{
-	DownstreamState = STATE_ERROR;
-}
-
 
-//Used by downstream class interfaces
+//Used by downstream class interfaces, and SPI interface
 void Downstream_PacketProcessor_FreakOut(void)
 {
 	DOWNSTREAM_STATEMACHINE_FREAKOUT;
@@ -212,6 +206,7 @@ void Downstream_HostUserCallback(USBH_HandleTypeDef *phost, uint8_t id)
 		//Unsupported device classes will cause a slow fault flash.
 		//This is distinct from the fast freakout flash caused by internal errors or attacks.
 		default:
+			USB_Host_Disconnect();
 			LED_Fault_SetBlinkRate(LED_SLOW_BLINK_RATE);
 			DownstreamState = STATE_ERROR;
 			return;
@@ -250,5 +245,16 @@ void Downstream_HostUserCallback(USBH_HandleTypeDef *phost, uint8_t id)
 		DOWNSTREAM_STATEMACHINE_FREAKOUT;
 		return;
 	}
+
+	//Called from main():
+	if (id == HOST_USER_CLASS_FAILED)
+	{
+		//Unsupported device classes will cause a slow fault flash.
+		//This is distinct from the fast freakout flash caused by internal errors or attacks.
+		USB_Host_Disconnect();
+		LED_Fault_SetBlinkRate(LED_SLOW_BLINK_RATE);
+		DownstreamState = STATE_ERROR;
+		return;
+	}
 }
 
diff --git a/Downstream/Src/usb_host.c b/Downstream/Src/usb_host.c
index ba4826c..4139c49 100644
--- a/Downstream/Src/usb_host.c
+++ b/Downstream/Src/usb_host.c
@@ -66,6 +66,12 @@ void USB_Host_Process()
 }
 
 
+//Called when Downstream Statemachine or SPI freaks out.
+void USB_Host_Disconnect()
+{
+	USBH_DeInit(&hUsbHostFS);
+}
+
 
 /**
   * @}