diff --git a/tests/extmod/uzlib_decompio.py b/tests/extmod/uzlib_decompio.py
new file mode 100644
index 0000000000..ee3204d07c
--- /dev/null
+++ b/tests/extmod/uzlib_decompio.py
@@ -0,0 +1,19 @@
+try:
+    import zlib
+except ImportError:
+    import uzlib as zlib
+import uio as io
+
+
+# Raw DEFLATE bitstream
+buf = io.BytesIO(b'\xcbH\xcd\xc9\xc9\x07\x00')
+inp = zlib.DecompIO(buf)
+print(buf.seek(0, 1))
+print(inp.read(1))
+print(buf.seek(0, 1))
+print(inp.read(2))
+print(inp.read())
+print(buf.seek(0, 1))
+print(inp.read(1))
+print(inp.read())
+print(buf.seek(0, 1))
diff --git a/tests/extmod/uzlib_decompio.py.exp b/tests/extmod/uzlib_decompio.py.exp
new file mode 100644
index 0000000000..6ef811d7db
--- /dev/null
+++ b/tests/extmod/uzlib_decompio.py.exp
@@ -0,0 +1,9 @@
+0
+b'h'
+2
+b'el'
+b'lo'
+7
+b''
+b''
+7