Index: src/runtime/sparsearray.m
==================================================================
--- src/runtime/sparsearray.m
+++ src/runtime/sparsearray.m
@@ -105,11 +105,11 @@
 				obj = src->buckets[i]->buckets[j]->buckets[k];
 
 				if (obj == NULL)
 					continue;
 
-				idx = (i << 16) | (j << 8) | k;
+				idx = (uint32_t)((i << 16) | (j << 8) | k);
 				objc_sparsearray_set(dst, idx, obj);
 			}
 		}
 #else
 		for (j = 0; j < 256; j++) {