Index: uspace/app/mkexfat/mkexfat.c
===================================================================
--- uspace/app/mkexfat/mkexfat.c	(revision 552efe3a26a6b78c9b269466a95be52cd90f4b24)
+++ uspace/app/mkexfat/mkexfat.c	(revision 3467821788e12f8a63245c60900cb8ee0d2a47fa)
@@ -46,4 +46,5 @@
 #include <sys/types.h>
 #include <sys/typefmt.h>
+#include <bool.h>
 #include "exfat.h"
 #include "upcase.h"
@@ -436,4 +437,5 @@
 	unsigned long allocated_cls;
 	int rc = EOK;
+	bool need_reset = true;
 
 	/* Bitmap size in sectors */
@@ -447,5 +449,8 @@
 
 	for (sec = 0; sec < bss; ++sec) {
-		memset(bitmap, 0, cfg->sector_size);
+		if (need_reset) {
+			need_reset = false;
+			memset(bitmap, 0, cfg->sector_size);
+		}
 		if (allocated_cls > 0) {
 			for (i = 0; i < allocated_cls; ++i) {
@@ -459,4 +464,5 @@
 
 			allocated_cls -= i;
+			need_reset = true;
 		}