diff --git a/cmd/mesh-controller/first_builds.go b/cmd/mesh-controller/first_builds.go
index aeda9d21..64c877de 100644
--- a/cmd/mesh-controller/first_builds.go
+++ b/cmd/mesh-controller/first_builds.go
@@ -164,7 +164,7 @@ func firstBuildsOf(ctx context.Context, inv catalogueReader, m link.SourceMoved,
 }
 
 // probeFirstBuildsID is the probe that reads the first merges waiting for mesh-delivery's word.
-const probeFirstBuildsID = "D17"
+const probeFirstBuildsID = "D18"
 
 // kindFirstBuildUnasked is what a first merge waiting too long for mesh-delivery's word raises.
 const kindFirstBuildUnasked = "first-build-unasked"