diff --git a/src/runtime/hashmap_fast.go b/src/runtime/hashmap_fast.go
index 67b9787909..6f21624d32 100644
--- a/src/runtime/hashmap_fast.go
+++ b/src/runtime/hashmap_fast.go
@@ -635,8 +635,8 @@ again:
 			if b.tophash[i] != top {
 				if b.tophash[i] == empty && inserti == nil {
 					inserti = &b.tophash[i]
-					insertk = add(unsafe.Pointer(b), dataOffset+i*uintptr(t.keysize))
-					val = add(unsafe.Pointer(b), dataOffset+bucketCnt*uintptr(t.keysize)+i*uintptr(t.valuesize))
+					insertk = add(unsafe.Pointer(b), dataOffset+i*2*sys.PtrSize)
+					val = add(unsafe.Pointer(b), dataOffset+bucketCnt*2*sys.PtrSize+i*uintptr(t.valuesize))
 				}
 				continue
 			}