diff --git a/build-relocatable-install.py b/build-relocatable-install.py
index 1bd87dac0dd2bf547f5547d39153cedaced72e3f..e15fd88d46a8a23db4a411c0cd9ac29894c680b3 100755
--- a/build-relocatable-install.py
+++ b/build-relocatable-install.py
@@ -450,6 +450,7 @@ def main():
             writer.write(
                 '#Package[:Architecture]\t#Version\t#Source\t#Installed-Size\n'
             )
+            writer.flush()
             v_check_call([
                 'dpkg-query',
                 '-W',