diff --git a/src/net/splice_test.go b/src/net/splice_test.go
index e2a6638e8f..0ba2f164c2 100644
--- a/src/net/splice_test.go
+++ b/src/net/splice_test.go
@@ -369,6 +369,7 @@ func startSpliceClient(conn Conn, op string, chunkSize, totalSize int) (func(),
 		"GO_NET_TEST_SPLICE_OP=" + op,
 		"GO_NET_TEST_SPLICE_CHUNK_SIZE=" + strconv.Itoa(chunkSize),
 		"GO_NET_TEST_SPLICE_TOTAL_SIZE=" + strconv.Itoa(totalSize),
+		"TMPDIR=" + os.Getenv("TMPDIR"),
 	}
 	cmd.ExtraFiles = append(cmd.ExtraFiles, f)
 	cmd.Stdout = os.Stdout