diff --git a/inc/ti/fn/fnbitcount.h b/inc/ti/fn/fnbitcount.h
index 7a114135..0eb0e4de 100644
--- a/inc/ti/fn/fnbitcount.h
+++ b/inc/ti/fn/fnbitcount.h
@@ -16,11 +16,10 @@ static int do__f_bit_count(ti_query_t * query, cleri_node_t * nd, ex_t * e)
     v = i < 0 ? 0-(uint64_t)i : (uint64_t)i;
 
     // from http://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetParallel
-    c = v - ((v >> 1) & 0x55555555);
-    c = ((c >> 2) & 0x33333333) + (c & 0x33333333);
-    c = ((c >> 4) + c) & 0x0F0F0F0F;
-    c = ((c >> 8) + c) & 0x00FF00FF;
-    c = ((c >> 16) + c) & 0x0000FFFF;
+    v = v - ((v >> 1) & (uint64_t)~(uint64_t)0/3);
+    v = (v & (uint64_t)~(uint64_t)0/15*3) + ((v >> 2) & (uint64_t)~(uint64_t)0/15*3);
+    v = (v + (v >> 4)) & (uint64_t)~(uint64_t)0/255*15;
+    c = (uint64_t)(v * ((uint64_t)~(uint64_t)0/255)) >> (sizeof(uint64_t) - 1) * CHAR_BIT;
 
     ti_val_unsafe_drop(query->rval);
 
diff --git a/itest/test_collection_functions.py b/itest/test_collection_functions.py
index 188434e1..998e241d 100755
--- a/itest/test_collection_functions.py
+++ b/itest/test_collection_functions.py
@@ -5957,9 +5957,13 @@ async def test_bit_count(self, client):
         res = await client.query("""//ti
             range(-1000, 1000).map(|i| i.bit_count());
         """)
-
         self.assertEqual(res, [i.bit_count() for i in range(-1000, 1000)])
 
+        res = await client.query("""//ti
+            ((5 << 60) + 5).bit_count();
+        """)
+        self.assertEqual(res, 4)
+
 
 if __name__ == '__main__':
     run_test(TestCollectionFunctions())