diff --git a/CHANGE_LOG b/CHANGE_LOG
index bdbdcadb..efb1cc09b 100644
--- a/CHANGE_LOG
+++ b/CHANGE_LOG
@@ -1,5 +1,6 @@
 2021-XX-XX   2.1.1:
 -------------------
+  * add tests
 
 
 2021-05-05   2.1.0:
diff --git a/README.rst b/README.rst
index 0ba66b30..bc58aab6 100644
--- a/README.rst
+++ b/README.rst
@@ -70,7 +70,7 @@ Once you have installed the package, you may want to test it:
     .........................................................................
     .............................................................
     ----------------------------------------------------------------------
-    Ran 336 tests in 0.332s
+    Ran 339 tests in 0.329s
 
     OK
 
diff --git a/bitarray/_bitarray.c b/bitarray/_bitarray.c
index 8eafb198..830bb8db 100644
--- a/bitarray/_bitarray.c
+++ b/bitarray/_bitarray.c
@@ -1760,8 +1760,8 @@ delslice(bitarrayobject *self, PyObject *slice)
         step = -step;
     }
     assert(step > 0 && start <= stop && slicelength > 0);
-    assert(start >= 0 && start < self->nbits);
-    assert(stop >= 0 && stop <= self->nbits);
+    assert(0 <= start && start < self->nbits);
+    assert(0 <= stop && stop <= self->nbits);
 
     if (step == 1) {
         assert(stop - start == slicelength);