diff --git a/docs/node-mixin/rules/rules.libsonnet b/docs/node-mixin/rules/rules.libsonnet
index 551810e7..154bb9d0 100644
--- a/docs/node-mixin/rules/rules.libsonnet
+++ b/docs/node-mixin/rules/rules.libsonnet
@@ -42,6 +42,16 @@
             expr: |||
               1 - (
                 node_memory_MemAvailable_bytes{%(nodeExporterSelector)s}
+                or
+                (
+                  node_memory_Buffers_bytes{%(nodeExporterSelector)s}
+                  +
+                  node_memory_Cached_bytes{%(nodeExporterSelector)s}
+                  +
+                  node_memory_MemFree_bytes{%(nodeExporterSelector)s}
+                  +
+                  node_memory_Slab_bytes{%(nodeExporterSelector)s}
+                )
               /
                 node_memory_MemTotal_bytes{%(nodeExporterSelector)s}
               )