Index: firmware/App/Services/TDInterface.c
===================================================================
diff -u -rb212425c0c7e9b69b4de7d46dd41030dfc3efa62 -rac1e1a4ff4312f4d99fdf26649a03b036de16e1c
--- firmware/App/Services/TDInterface.c	(.../TDInterface.c)	(revision b212425c0c7e9b69b4de7d46dd41030dfc3efa62)
+++ firmware/App/Services/TDInterface.c	(.../TDInterface.c)	(revision ac1e1a4ff4312f4d99fdf26649a03b036de16e1c)
@@ -342,14 +342,23 @@
     {
         PRE_GEN_DIALYSATE_REQ_PAYLOAD_T startPreGenRequest;
         DD_OP_MODE_T ddMode = getCurrentOperationMode();
+        FP_OP_MODE_T fpMode = getCurrentFPOperationMode();
 
         memcpy( &startPreGenRequest, message->payload, sizeof( PRE_GEN_DIALYSATE_REQ_PAYLOAD_T ) );
 
         // Process the pre-gen dialysate delivery request message
         if ( ( DD_MODE_STAN == ddMode ) && ( TRUE == startPreGenRequest.start ) )
         {
             // Start FP Pre-Generate Permeate
-            fpReason = signalStartGenPermeate();
+
+            if ( FP_MODE_STAN == fpMode )
+            {
+                fpReason = signalStartGenPermeate();
+            }
+            else
+            {
+                fpReason = REQUEST_REJECT_REASON_NOT_ALLOWED_IN_CURRENT_MODE;
+            }
             // start pre-gen dialysate
             result = requestDDPreGenStart();