diff --git a/etc/git/post-merge b/etc/git/post-merge
index f2ad37d35c..9f116dd3e9 100755
--- a/etc/git/post-merge
+++ b/etc/git/post-merge
@@ -1,3 +1,9 @@
 #!/bin/sh
 # Authenticate the repo upon 'git pull' and similar.
-exec guix git authenticate
+if ! git config guix.authentication.introduction-commit; then
+    exec guix git authenticate 9edb3f66fd807b096b48283debdcddccfea34bad \
+         "BBB0 2DDF 2CEA F6A8 0D1D  E643 A2A0 6DF2 A33A 54FA" \
+         -k origin/keyring
+else
+    exec guix git authenticate
+fi