diff --git a/armsrc/appmain.c b/armsrc/appmain.c
index ecf22adfe..f69bdccc1 100644
--- a/armsrc/appmain.c
+++ b/armsrc/appmain.c
@@ -568,11 +568,14 @@ void ListenReaderField(int limit)
 void UsbPacketReceived(BYTE *packet, int len)
 {
 	UsbCommand *c = (UsbCommand *)packet;
+	UsbCommand ack;
 
 	switch(c->cmd) {
 #ifdef WITH_LF
 		case CMD_ACQUIRE_RAW_ADC_SAMPLES_125K:
 			AcquireRawAdcSamples125k(c->arg[0]);
+			ack.cmd = CMD_ACK;
+			UsbSendPacket((BYTE*)&ack, sizeof(ack));
 			break;
 #endif
 
@@ -719,7 +722,6 @@ void UsbPacketReceived(BYTE *packet, int len)
 		}
 
 		case CMD_DOWNLOADED_SIM_SAMPLES_125K: {
-			UsbCommand ack;
 			BYTE *b = (BYTE *)BigBuf;
 			memcpy(b+c->arg[0], c->d.asBytes, 48);
 			//Dbprintf("copied 48 bytes to %i",b+c->arg[0]);
diff --git a/client/cmdlf.c b/client/cmdlf.c
index e82e48aef..26bd5e4fd 100644
--- a/client/cmdlf.c
+++ b/client/cmdlf.c
@@ -266,6 +266,7 @@ int CmdLFRead(const char *Cmd)
     return 0;
   }
   SendCommand(&c);
+  WaitForResponse(CMD_ACK);
   return 0;
 }
 
diff --git a/client/cmdmain.c b/client/cmdmain.c
index 3cdcd0893..30b431f55 100644
--- a/client/cmdmain.c
+++ b/client/cmdmain.c
@@ -125,6 +125,7 @@ void UsbCommandReceived(UsbCommand *UC)
       for(i=0; i<48; i++) sample_buf[i] = UC->d.asBytes[i];
       received_command = UC->cmd;
       return;
+    case CMD_ACQUIRE_RAW_ADC_SAMPLES_125K:
     case CMD_DOWNLOADED_SIM_SAMPLES_125K:
       if (UC->cmd != CMD_ACK) goto unexpected_response;
       // got ACK