diff --git a/solr/CHANGES.txt b/solr/CHANGES.txt
index e628694cca6..b4196edd847 100644
--- a/solr/CHANGES.txt
+++ b/solr/CHANGES.txt
@@ -313,6 +313,8 @@ Bug Fixes
 * SOLR-10218: The Schema API commands "add-field-type" and "replace-field-type" improperly specify SimilarityFactory params.
   (Benjamin Deininger, Troy Mohl, Steve Rowe)
 
+* SOLR-10319: SolrCore "instanceDir" metric not visible in JMX. (ab)
+
 Optimizations
 ----------------------
 
diff --git a/solr/core/src/java/org/apache/solr/core/SolrCore.java b/solr/core/src/java/org/apache/solr/core/SolrCore.java
index 6e25280c653..9d77c7e2651 100644
--- a/solr/core/src/java/org/apache/solr/core/SolrCore.java
+++ b/solr/core/src/java/org/apache/solr/core/SolrCore.java
@@ -1134,7 +1134,7 @@ public final class SolrCore implements SolrInfoMBean, SolrMetricProducer, Closea
     manager.registerGauge(registry, () -> name == null ? "(null)" : name, true, "coreName", Category.CORE.toString());
     manager.registerGauge(registry, () -> startTime, true, "startTime", Category.CORE.toString());
     manager.registerGauge(registry, () -> getOpenCount(), true, "refCount", Category.CORE.toString());
-    manager.registerGauge(registry, () -> resourceLoader.getInstancePath(), true, "instanceDir", Category.CORE.toString());
+    manager.registerGauge(registry, () -> resourceLoader.getInstancePath().toString(), true, "instanceDir", Category.CORE.toString());
     manager.registerGauge(registry, () -> getIndexDir(), true, "indexDir", Category.CORE.toString());
     manager.registerGauge(registry, () -> getIndexSize(), true, "sizeInBytes", Category.INDEX.toString());
     manager.registerGauge(registry, () -> NumberUtils.readableSize(getIndexSize()), true, "size", Category.INDEX.toString());