diff --git a/pkg/spiffs/fs/spiffs_fs.c b/pkg/spiffs/fs/spiffs_fs.c
index 33f37fb49f68..17244bd2a6c8 100644
--- a/pkg/spiffs/fs/spiffs_fs.c
+++ b/pkg/spiffs/fs/spiffs_fs.c
@@ -14,7 +14,7 @@
 
 #include "kernel_defines.h"
 
-#define ENABLE_DEBUG (0)
+#define ENABLE_DEBUG (1)
 #include <debug.h>
 
 static int spiffs_err_to_errno(s32_t err);
@@ -26,7 +26,12 @@ static int32_t _dev_read(struct spiffs_t *fs, u32_t addr, u32_t size, u8_t *dst)
 
     //DEBUG("spiffs: read: from addr 0x%" PRIx32 " size 0x%" PRIx32 "\n", addr, size);
 
-    return mtd_read(dev, dst, addr, size);
+    if (mtd_read(dev, dst, addr, size) > 0) {
+        return 0;
+    }
+    else {
+        return -EIO;
+    }
 }
 
 static int32_t _dev_write(struct spiffs_t *fs, u32_t addr, u32_t size, u8_t *src)
@@ -35,7 +40,12 @@ static int32_t _dev_write(struct spiffs_t *fs, u32_t addr, u32_t size, u8_t *src
 
     DEBUG("spiffs: write: from addr 0x%" PRIx32 " size 0x%" PRIx32 "\n", addr, size);
 
-    return mtd_write(dev, src, addr, size);
+    if (mtd_write(dev, src, addr, size) > 0) {
+        return 0;
+    }
+    else {
+        return -EIO;
+    }
 }
 
 static int32_t _dev_erase(struct spiffs_t *fs, u32_t addr, u32_t size)