diff --git a/pkg/spiffs/fs/spiffs_fs.c b/pkg/spiffs/fs/spiffs_fs.c
index 2549f8f70d..73c0170351 100644
--- a/pkg/spiffs/fs/spiffs_fs.c
+++ b/pkg/spiffs/fs/spiffs_fs.c
@@ -136,10 +136,16 @@ static int prepare(spiffs_desc_t *fs_desc)
 #if SPIFFS_SINGLETON == 0
     DEBUG("spiffs: mount: mtd page_size=%" PRIu32 ", pages_per_sector=%" PRIu32
           ", sector_count=%" PRIu32 "\n", dev->page_size, dev->pages_per_sector, dev->sector_count);
-    fs_desc->config.phys_size = dev->page_size * dev->pages_per_sector * dev->sector_count;
+    uint32_t sector_count = (fs_desc->block_count == 0) ? dev->sector_count : fs_desc->block_count;
+    /* inside memory area */
+    assert(((fs_desc->base_addr / (dev->page_size * dev->pages_per_sector)) + sector_count)
+           <= dev->sector_count);
+    /* base addr is aligned on a sector */
+    assert(fs_desc->base_addr % (dev->pages_per_sector * dev->page_size) == 0);
+    fs_desc->config.phys_size = dev->page_size * dev->pages_per_sector * sector_count;
     fs_desc->config.log_block_size = dev->page_size * dev->pages_per_sector;
     fs_desc->config.log_page_size = dev->page_size;
-    fs_desc->config.phys_addr = 0;
+    fs_desc->config.phys_addr = fs_desc->base_addr;
     fs_desc->config.phys_erase_block = dev->page_size * dev->pages_per_sector;
 #endif
 
diff --git a/sys/include/fs/spiffs_fs.h b/sys/include/fs/spiffs_fs.h
index 9cb3932bc9..caa305ad6b 100644
--- a/sys/include/fs/spiffs_fs.h
+++ b/sys/include/fs/spiffs_fs.h
@@ -116,6 +116,11 @@ typedef struct spiffs_desc {
 #if (SPIFFS_HAL_CALLBACK_EXTRA == 1) || defined(DOXYGEN)
     mtd_dev_t *dev;                             /**< The underlying mtd device, must be set by user */
 #endif
+#if (SPIFFS_SINGLETON == 0) || defined(DOXYGEN)
+    uint32_t base_addr;                         /**< Base address of partition */
+    uint32_t block_count;                       /**< Number of blocks in current partition,
+                                                 *  if 0, the mtd number of sector is used */
+#endif
 } spiffs_desc_t;
 
 /** The SPIFFS vfs driver, a pointer to a spiffs_desc_t must be provided as vfs_mountp::private_data */