diff --git a/lucene/test-framework/src/java/org/apache/lucene/tests/index/BaseIndexFileFormatTestCase.java b/lucene/test-framework/src/java/org/apache/lucene/tests/index/BaseIndexFileFormatTestCase.java
index 297c1b777f5..c2aa7ff0e4d 100644
--- a/lucene/test-framework/src/java/org/apache/lucene/tests/index/BaseIndexFileFormatTestCase.java
+++ b/lucene/test-framework/src/java/org/apache/lucene/tests/index/BaseIndexFileFormatTestCase.java
@@ -275,6 +275,9 @@ public void testMergeStability() throws Exception {
         new IndexWriterConfig(new MockAnalyzer(random()))
             .setUseCompoundFile(false)
             .setMergePolicy(mp);
+    if (VERBOSE) {
+      cfg.setInfoStream(System.out);
+    }
     IndexWriter w = new IndexWriter(dir, cfg);
     final int numDocs = atLeast(500);
     for (int i = 0; i < numDocs; ++i) {
diff --git a/lucene/test-framework/src/java/org/apache/lucene/tests/index/BaseKnnVectorsFormatTestCase.java b/lucene/test-framework/src/java/org/apache/lucene/tests/index/BaseKnnVectorsFormatTestCase.java
index 752f21ea5d7..97b578e7c5c 100644
--- a/lucene/test-framework/src/java/org/apache/lucene/tests/index/BaseKnnVectorsFormatTestCase.java
+++ b/lucene/test-framework/src/java/org/apache/lucene/tests/index/BaseKnnVectorsFormatTestCase.java
@@ -124,6 +124,14 @@ protected void addRandomFields(Document doc) {
     }
   }
 
+  @Override
+  protected boolean mergeIsStable() {
+    // suppress this test from base class: merges for knn graphs are not stable due to connected
+    // components
+    // logic
+    return false;
+  }
+
   private int getVectorsMaxDimensions(String fieldName) {
     return Codec.getDefault().knnVectorsFormat().getMaxDimensions(fieldName);
   }