diff --git a/tests/extmod/uhashlib_sha1.py b/tests/extmod/uhashlib_sha1.py
index 4f7066899a..9d6427b33f 100644
--- a/tests/extmod/uhashlib_sha1.py
+++ b/tests/extmod/uhashlib_sha1.py
@@ -19,3 +19,10 @@ except AttributeError:
 sha1 = hashlib.sha1(b'hello')
 sha1.update(b'world')
 print(sha1.digest())
+
+sha1 = hashlib.sha1(b'hello')
+try:
+    sha1.update(u'world')
+except TypeError as e:
+    print("TypeError")
+print(sha1.digest())
diff --git a/tests/extmod/uhashlib_sha256.py b/tests/extmod/uhashlib_sha256.py
index 3200e8f5cd..0322c20de4 100644
--- a/tests/extmod/uhashlib_sha256.py
+++ b/tests/extmod/uhashlib_sha256.py
@@ -23,6 +23,13 @@ print(h.digest())
 
 print(hashlib.sha256(b"\xff" * 64).digest())
 
+sha256 = hashlib.sha256(b'hello')
+try:
+    sha256.update(u'world')
+except TypeError as e:
+    print("TypeError")
+print(sha256.digest())
+
 # TODO: running .digest() several times in row is not supported()
 #h = hashlib.sha256(b'123')
 #print(h.digest())