diff --git a/firmware/hackrf_usb/usb_api_sweep.c b/firmware/hackrf_usb/usb_api_sweep.c
index 581faacc..503e7f6a 100644
--- a/firmware/hackrf_usb/usb_api_sweep.c
+++ b/firmware/hackrf_usb/usb_api_sweep.c
@@ -34,6 +34,7 @@
 #define MIN_FREQ 1
 #define MAX_FREQ 6000
 #define MAX_FREQ_COUNT 1000
+#define THROWAWAY_BUFFERS 2
 
 volatile bool start_sweep_mode = false;
 static uint64_t sweep_freq;
@@ -89,16 +90,18 @@ void sweep_mode(void) {
 		if (transfer) {
 			*(uint16_t*)buffer = 0x7F7F;
 			*(uint16_t*)(buffer+2) = sweep_freq;
-			usb_transfer_schedule_block(
-				&usb_endpoint_bulk_in,
-				buffer,
-				0x4000,
-				NULL, NULL
-			);
+			if (blocks_queued > THROWAWAY_BUFFERS) {
+				usb_transfer_schedule_block(
+					&usb_endpoint_bulk_in,
+					buffer,
+					0x4000,
+					NULL, NULL
+				);
+			}
 			transfer = false;
 		}
 
-		if (blocks_queued >= dwell_blocks) {
+		if ((dwell_blocks + THROWAWAY_BUFFERS) <= blocks_queued) {
 			if(++ifreq >= frequency_count)
 				ifreq = 0;
 			sweep_freq = frequencies[ifreq];
diff --git a/host/hackrf-tools/src/hackrf_sweep.c b/host/hackrf-tools/src/hackrf_sweep.c
index 6c044203..13a9c64d 100644
--- a/host/hackrf-tools/src/hackrf_sweep.c
+++ b/host/hackrf-tools/src/hackrf_sweep.c
@@ -243,7 +243,7 @@ static void usage() {
 	fprintf(stderr, "\t[-l gain_db] # RX LNA (IF) gain, 0-40dB, 8dB steps\n");
 	fprintf(stderr, "\t[-g gain_db] # RX VGA (baseband) gain, 0-62dB, 2dB steps\n");
 	fprintf(stderr, "\t[-x gain_db] # TX VGA (IF) gain, 0-47dB, 1dB steps\n");
-	fprintf(stderr, "\t[-n num_samples] # Number of samples per frequency, 0-4294967296\n");
+	fprintf(stderr, "\t[-n num_samples] # Number of samples per frequency, 16384-4294967296\n");
 }
 
 static hackrf_device* device = NULL;
@@ -355,6 +355,11 @@ int main(int argc, char** argv) {
 		return EXIT_FAILURE;
 	}
 
+	if (num_samples < 0x4000) {
+		fprintf(stderr, "warning: num_samples (-n) must be at least 16384\n");
+		return EXIT_FAILURE;
+	}
+
 	if( amp ) {
 		if( amp_enable > 1 ) {
 			fprintf(stderr, "argument error: amp_enable shall be 0 or 1.\n");