diff --git a/Modules/_collectionsmodule.c b/Modules/_collectionsmodule.c
--- a/Modules/_collectionsmodule.c
+++ b/Modules/_collectionsmodule.c
@@ -780,15 +780,15 @@
         b = deque->rightblock;
     } else {
         i += deque->leftindex;
-        n = (Py_ssize_t)((unsigned) i / BLOCKLEN);
-        i = (Py_ssize_t)((unsigned) i % BLOCKLEN);
+        n = (Py_ssize_t)((size_t) i / BLOCKLEN);
+        i = (Py_ssize_t)((size_t) i % BLOCKLEN);
         if (index < (Py_SIZE(deque) >> 1)) {
             b = deque->leftblock;
             while (n--)
                 b = b->rightlink;
         } else {
             n = (Py_ssize_t)(
-                    ((unsigned)(deque->leftindex + Py_SIZE(deque) - 1))
+                    ((size_t)(deque->leftindex + Py_SIZE(deque) - 1))
                     / BLOCKLEN - n);
             b = deque->rightblock;
             while (n--)
@@ -839,15 +839,15 @@
         return deque_del_item(deque, i);
 
     i += deque->leftindex;
-    n = (Py_ssize_t)((unsigned) i / BLOCKLEN);
-    i = (Py_ssize_t)((unsigned) i % BLOCKLEN);
+    n = (Py_ssize_t)((size_t) i / BLOCKLEN);
+    i = (Py_ssize_t)((size_t) i % BLOCKLEN);
     if (index <= halflen) {
         b = deque->leftblock;
         while (n--)
             b = b->rightlink;
     } else {
         n = (Py_ssize_t)(
-                ((unsigned)(deque->leftindex + Py_SIZE(deque) - 1))
+                ((size_t)(deque->leftindex + Py_SIZE(deque) - 1))
                 / BLOCKLEN - n);
         b = deque->rightblock;
         while (n--)