diff --git a/asset/prometheus/quantus-rules.yml b/asset/prometheus/quantus-rules.yml
index f71c40d..a0fc2ed 100644
--- a/asset/prometheus/quantus-rules.yml
+++ b/asset/prometheus/quantus-rules.yml
@@ -2,8 +2,10 @@
 # /etc/prometheus/rules.d/quantus.yml on the metrics host (quantus/miner#9).
 #
 # The miner's series (job quantus-miner, instance host:9900) and the GPU
-# series from node-exporter's textfile collector (job node, `host` label) are
-# joined on a derived `host` and on `device` (the miner's engine index) =
+# series from node-exporter's textfile collector (job node, `host` label, the
+# SHORT hostname as cichlid's inventory sets it) are joined on `host` derived
+# as the first DNS label of the miner's instance, and on `device` (the miner's
+# engine index) =
 # `gpu` (nvidia-smi index). On single-card hosts both are 0; on a multi-card
 # host the engine orders adapters discrete-first as Vulkan enumerates them,
 # which is expected to match nvidia-smi's order but is not guaranteed.
@@ -13,7 +15,7 @@ groups:
     rules:
       # Per-device throughput, keyed so it can be joined with the GPU series.
       - record: quantus:device_hashrate:rate5m
-        expr: label_replace(rate(miner_device_hashes_total[5m]), "host", "$1", "instance", "([^:]+):.*")
+        expr: label_replace(rate(miner_device_hashes_total[5m]), "host", "$1", "instance", "([^.:]+).*")
 
       # The same, carrying the build that produced it. The series set changes
       # on every deploy, which is the annotation the dashboard draws.