diff --git a/tests/docker/docker.py b/tests/docker/docker.py
index 36b7868406..884dfeb29c 100755
--- a/tests/docker/docker.py
+++ b/tests/docker/docker.py
@@ -332,9 +332,9 @@ def build_image(self, tag, docker_dir, dockerfile,
                          (uname, uid, uname))
 
         tmp_df.write("\n")
-        tmp_df.write("LABEL com.qemu.dockerfile-checksum=%s" % (checksum))
+        tmp_df.write("LABEL com.qemu.dockerfile-checksum=%s\n" % (checksum))
         for f, c in extra_files_cksum:
-            tmp_df.write("LABEL com.qemu.%s-checksum=%s" % (f, c))
+            tmp_df.write("LABEL com.qemu.%s-checksum=%s\n" % (f, c))
 
         tmp_df.flush()