diff --git a/tests/extmod/vfs_fat_ramdisklarge.py b/tests/extmod/vfs_fat_ramdisklarge.py
new file mode 100644
index 0000000000..6f95910315
--- /dev/null
+++ b/tests/extmod/vfs_fat_ramdisklarge.py
@@ -0,0 +1,70 @@
+# test making a FAT filesystem on a very large block device
+
+try:
+    import uos
+except ImportError:
+    print("SKIP")
+    raise SystemExit
+
+try:
+    uos.VfsFat
+except AttributeError:
+    print("SKIP")
+    raise SystemExit
+
+
+class RAMBDevSparse:
+
+    SEC_SIZE = 512
+
+    def __init__(self, blocks):
+        self.blocks = blocks
+        self.data = {}
+
+    def readblocks(self, n, buf):
+        #print("readblocks(%s, %x(%d))" % (n, id(buf), len(buf)))
+        assert len(buf) == self.SEC_SIZE
+        if n not in self.data:
+            self.data[n] = bytearray(self.SEC_SIZE)
+        buf[:] = self.data[n]
+
+    def writeblocks(self, n, buf):
+        #print("writeblocks(%s, %x)" % (n, id(buf)))
+        mv = memoryview(buf)
+        for off in range(0, len(buf), self.SEC_SIZE):
+            s = n + off // self.SEC_SIZE
+            if s not in self.data:
+                self.data[s] = bytearray(self.SEC_SIZE)
+            self.data[s][:] = mv[off:off + self.SEC_SIZE]
+
+    def ioctl(self, op, arg):
+        #print("ioctl(%d, %r)" % (op, arg))
+        if op == 4:  # BP_IOCTL_SEC_COUNT
+            return self.blocks
+        if op == 5:  # BP_IOCTL_SEC_SIZE
+            return self.SEC_SIZE
+
+
+try:
+    bdev = RAMBDevSparse(4 * 1024 * 1024 * 1024 // RAMBDevSparse.SEC_SIZE)
+    uos.VfsFat.mkfs(bdev)
+except MemoryError:
+    print("SKIP")
+    raise SystemExit
+
+vfs = uos.VfsFat(bdev)
+uos.mount(vfs, "/ramdisk")
+
+print("statvfs:", vfs.statvfs("/ramdisk"))
+
+f = open('/ramdisk/test.txt', 'w')
+f.write('test file')
+f.close()
+
+print("statvfs:", vfs.statvfs("/ramdisk"))
+
+f = open('/ramdisk/test.txt')
+print(f.read())
+f.close()
+
+uos.umount(vfs)
diff --git a/tests/extmod/vfs_fat_ramdisklarge.py.exp b/tests/extmod/vfs_fat_ramdisklarge.py.exp
new file mode 100644
index 0000000000..ea723e2249
--- /dev/null
+++ b/tests/extmod/vfs_fat_ramdisklarge.py.exp
@@ -0,0 +1,3 @@
+statvfs: (32768, 32768, 131054, 131053, 131053, 0, 0, 0, 0, 255)
+statvfs: (32768, 32768, 131054, 131052, 131052, 0, 0, 0, 0, 255)
+test file