diff --git a/repos/os/src/test/terminal_expect_send/main.cc b/repos/os/src/test/terminal_expect_send/main.cc
index 623aea6882..2e679bc67d 100644
--- a/repos/os/src/test/terminal_expect_send/main.cc
+++ b/repos/os/src/test/terminal_expect_send/main.cc
@@ -55,6 +55,7 @@ struct Main
 			if (read_buffer[i] == '\n') {
 				if (verbose) log(Cstring(line));
 				line_idx = 0;
+				line[line_idx] = 0;
 			}
 		}
 	}