diff --git a/qdl.c b/qdl.c
index 7ba1991..106b19a 100644
--- a/qdl.c
+++ b/qdl.c
@@ -34,6 +34,7 @@
 #include <getopt.h>
 #include <stdbool.h>
 #include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
 #include <libxml/parser.h>
 #include <libxml/tree.h>
@@ -106,6 +107,10 @@ static void print_usage(void)
 		__progname);
 }
 
+enum {
+	OPT_OUT_CHUNK_SIZE = 1000,
+};
+
 int main(int argc, char **argv)
 {
 	char *prog_mbn, *storage="ufs";
@@ -115,12 +120,13 @@ int main(int argc, char **argv)
 	int ret;
 	int opt;
 	bool qdl_finalize_provisioning = false;
-
+	long out_chunk_size;
 
 	static struct option options[] = {
 		{"debug", no_argument, 0, 'd'},
 		{"include", required_argument, 0, 'i'},
 		{"finalize-provisioning", no_argument, 0, 'l'},
+		{"out-chunk-size", required_argument, 0, OPT_OUT_CHUNK_SIZE },
 		{"serial", required_argument, 0, 'S'},
 		{"storage", required_argument, 0, 's'},
 		{0, 0, 0, 0}
@@ -137,6 +143,10 @@ int main(int argc, char **argv)
 		case 'l':
 			qdl_finalize_provisioning = true;
 			break;
+		case OPT_OUT_CHUNK_SIZE:
+			out_chunk_size = strtol(optarg, NULL, 10);
+			qdl_set_out_chunk_size(&qdl, out_chunk_size);
+			break;
 		case 's':
 			storage = optarg;
 			break;
diff --git a/qdl.h b/qdl.h
index 9d6d58d..c2ed0d7 100644
--- a/qdl.h
+++ b/qdl.h
@@ -21,6 +21,7 @@ struct qdl_device {
 
         size_t in_maxpktsize;
         size_t out_maxpktsize;
+        size_t out_chunk_size;
 
         char *mappings[MAPPING_SZ]; // array index is the id from the device
 };
@@ -28,6 +29,7 @@ struct qdl_device {
 int qdl_open(struct qdl_device *qdl, const char *serial);
 int qdl_read(struct qdl_device *qdl, void *buf, size_t len, unsigned int timeout);
 int qdl_write(struct qdl_device *qdl, const void *buf, size_t len);
+void qdl_set_out_chunk_size(struct qdl_device *qdl, long size);
 
 int firehose_run(struct qdl_device *qdl, const char *incdir, const char *storage);
 int sahara_run(struct qdl_device *qdl, char *img_arr[], bool single_image,
diff --git a/usb.c b/usb.c
index 381cfa3..cda5e74 100644
--- a/usb.c
+++ b/usb.c
@@ -10,6 +10,8 @@
 
 #include "qdl.h"
 
+#define DEFAULT_OUT_CHUNK_SIZE (1024 * 1024)
+
 /*
  * libusb commit f0cce43f882d ("core: Fix definition and use of enum
  * libusb_transfer_type") split transfer type and endpoint transfer types.
@@ -141,6 +143,20 @@ static int qdl_try_open(libusb_device *dev, struct qdl_device *qdl, const char *
 		qdl->in_maxpktsize = in_size;
 		qdl->out_maxpktsize = out_size;
 
+		if (qdl->out_chunk_size && qdl->out_chunk_size % out_size) {
+			fprintf(stderr,
+				"WARNING: requested out-chunk-size must be multiple of the device's wMaxPacketSize %ld, using %ld\n",
+				out_size, out_size);
+			qdl->out_chunk_size = out_size;
+		} else if (!qdl->out_chunk_size) {
+			qdl->out_chunk_size = DEFAULT_OUT_CHUNK_SIZE;
+		}
+
+		if (qdl_debug) {
+			fprintf(stderr, "USB: using out-chunk-size of %ld\n",
+				qdl->out_chunk_size);
+		}
+
 		return 1;
 	}
 
@@ -215,7 +231,7 @@ int qdl_write(struct qdl_device *qdl, const void *buf, size_t len)
 	int ret;
 
 	while (len > 0) {
-		xfer = (len > qdl->out_maxpktsize) ? qdl->out_maxpktsize : len;
+		xfer = (len > qdl->out_chunk_size) ? qdl->out_chunk_size : len;
 
 		ret = libusb_bulk_transfer(qdl->usb_handle, qdl->out_ep, data,
 					   xfer, &actual, 1000);
@@ -239,3 +255,8 @@ int qdl_write(struct qdl_device *qdl, const void *buf, size_t len)
 
 	return count;
 }
+
+void qdl_set_out_chunk_size(struct qdl_device *qdl, long size)
+{
+	qdl->out_chunk_size = size;
+}