Index: src/runtime/sparsearray.m
==================================================================
--- src/runtime/sparsearray.m
+++ src/runtime/sparsearray.m
@@ -119,11 +119,11 @@
 			obj = src->buckets[i]->buckets[j];
 
 			if (obj == NULL)
 				continue;
 
-			idx = (i << 8) | j;
+			idx = (uint32_t)((i << 8) | j);
 			objc_sparsearray_set(dst, idx, obj);
 		}
 #endif
 	}
 }