diff --git a/drivers/mtd/ubi/build.c b/drivers/mtd/ubi/build.c
index e26fe12b1aae..9690cf9aaef5 100644
--- a/drivers/mtd/ubi/build.c
+++ b/drivers/mtd/ubi/build.c
@@ -81,6 +81,7 @@ static struct mtd_dev_param __initdata mtd_dev_param[UBI_MAX_DEVICES];
 #ifdef CONFIG_MTD_UBI_FASTMAP
 /* UBI module parameter to enable fastmap automatically on non-fastmap images */
 static bool fm_autoconvert;
+static bool fm_debug;
 #endif
 /* Root UBI "class" object (corresponds to '/<sysfs>/class/ubi/') */
 struct class *ubi_class;
@@ -951,6 +952,8 @@ int ubi_attach_mtd_dev(struct mtd_info *mtd, int ubi_num,
 
 	ubi->fm_wl_pool.max_size = ubi->fm_pool.max_size / 2;
 	ubi->fm_disabled = !fm_autoconvert;
+	if (fm_debug)
+		ubi_enable_dbg_chk_fastmap(ubi);
 
 	if (!ubi->fm_disabled && (int)mtd_div_by_eb(ubi->mtd->size, ubi->mtd)
 	    <= UBI_FM_MAX_START) {
@@ -1503,6 +1506,8 @@ MODULE_PARM_DESC(mtd, "MTD devices to attach. Parameter format: mtd=<name|num|pa
 #ifdef CONFIG_MTD_UBI_FASTMAP
 module_param(fm_autoconvert, bool, 0644);
 MODULE_PARM_DESC(fm_autoconvert, "Set this parameter to enable fastmap automatically on images without a fastmap.");
+module_param(fm_debug, bool, 0);
+MODULE_PARM_DESC(fm_debug, "Set this parameter to enable fastmap debugging by default. Warning, this will make fastmap slow!");
 #endif
 MODULE_VERSION(__stringify(UBI_VERSION));
 MODULE_DESCRIPTION("UBI - Unsorted Block Images");
diff --git a/drivers/mtd/ubi/debug.h b/drivers/mtd/ubi/debug.h
index e99ef37a321e..c6ea4431acf3 100644
--- a/drivers/mtd/ubi/debug.h
+++ b/drivers/mtd/ubi/debug.h
@@ -132,4 +132,9 @@ static inline int ubi_dbg_chk_fastmap(const struct ubi_device *ubi)
 {
 	return ubi->dbg.chk_fastmap;
 }
+
+static inline void ubi_enable_dbg_chk_fastmap(struct ubi_device *ubi)
+{
+	ubi->dbg.chk_fastmap = 1;
+}
 #endif /* !__UBI_DEBUG_H__ */