diff --git a/solr/core/src/java/org/apache/solr/index/WrapperMergePolicyFactory.java b/solr/core/src/java/org/apache/solr/index/WrapperMergePolicyFactory.java
index 24ba2378159..61088a8dbc0 100644
--- a/solr/core/src/java/org/apache/solr/index/WrapperMergePolicyFactory.java
+++ b/solr/core/src/java/org/apache/solr/index/WrapperMergePolicyFactory.java
@@ -16,7 +16,9 @@
  */
 package org.apache.solr.index;
 
+import java.util.HashSet;
 import java.util.Iterator;
+import java.util.Set;
 
 import org.apache.lucene.index.MergePolicy;
 import org.apache.solr.core.SolrResourceLoader;
@@ -34,10 +36,26 @@ public abstract class WrapperMergePolicyFactory extends MergePolicyFactory {
   static final String WRAPPED_PREFIX = "wrapped.prefix"; // not private so that test(s) can use it
 
   private final MergePolicyFactoryArgs wrappedMergePolicyArgs;
+  private final String wrappedMergePolicyClassName;
 
   protected WrapperMergePolicyFactory(SolrResourceLoader resourceLoader, MergePolicyFactoryArgs args, IndexSchema schema) {
     super(resourceLoader, args, schema);
     wrappedMergePolicyArgs = filterWrappedMergePolicyFactoryArgs();
+    if (wrappedMergePolicyArgs == null) {
+      wrappedMergePolicyClassName = null;
+    } else {
+      wrappedMergePolicyClassName = (String) wrappedMergePolicyArgs.remove(CLASS);
+      if (wrappedMergePolicyClassName == null) {
+        throw new IllegalArgumentException("Class name not defined for wrapped MergePolicyFactory!");
+      }
+    }
+    if (wrappedMergePolicyArgs != null) {
+      final Set<String> overshadowedWrappedMergePolicyArgs = new HashSet<>(wrappedMergePolicyArgs.keys());
+      overshadowedWrappedMergePolicyArgs.retainAll(args.keys());
+      if (!overshadowedWrappedMergePolicyArgs.isEmpty()) {
+        throw new IllegalArgumentException("Wrapping and wrapped merge policy args overlap! "+overshadowedWrappedMergePolicyArgs);
+      }
+    }
   }
 
   /**
@@ -55,13 +73,8 @@ public abstract class WrapperMergePolicyFactory extends MergePolicyFactory {
       return getDefaultWrappedMergePolicy();
     }
 
-    final String className = (String) wrappedMergePolicyArgs.remove(CLASS);
-    if (className == null) {
-      throw new IllegalArgumentException("Class name not defined for wrapped MergePolicyFactory!");
-    }
-
     final MergePolicyFactory mpf = resourceLoader.newInstance(
-        className,
+        wrappedMergePolicyClassName,
         MergePolicyFactory.class,
         NO_SUB_PACKAGES,
         new Class[] {SolrResourceLoader.class, MergePolicyFactoryArgs.class, IndexSchema.class},
diff --git a/solr/core/src/test/org/apache/solr/index/WrapperMergePolicyFactoryTest.java b/solr/core/src/test/org/apache/solr/index/WrapperMergePolicyFactoryTest.java
index cd904f5455f..e4c7b3dc83e 100644
--- a/solr/core/src/test/org/apache/solr/index/WrapperMergePolicyFactoryTest.java
+++ b/solr/core/src/test/org/apache/solr/index/WrapperMergePolicyFactoryTest.java
@@ -19,6 +19,7 @@ package org.apache.solr.index;
 import org.apache.lucene.index.MergePolicy;
 import org.apache.lucene.index.NoMergePolicy;
 import org.apache.lucene.index.TieredMergePolicy;
+import org.apache.lucene.index.UpgradeIndexMergePolicy;
 import org.apache.solr.SolrTestCaseJ4;
 import org.apache.solr.core.SolrResourceLoader;
 import org.apache.solr.schema.IndexSchema;
@@ -68,6 +69,48 @@ public class WrapperMergePolicyFactoryTest extends SolrTestCaseJ4 {
     assertEquals("maxMergedSegmentMB", testMaxMergedSegmentMB, tmp.getMaxMergedSegmentMB(), 0.0d);
   }
 
+  public void testUpgradeIndexMergePolicyFactory() {
+    final int N = 10;
+    final Double wrappingNoCFSRatio = random().nextBoolean() ? null : random().nextInt(N+1)/((double)N); // must be: 0.0 <= value <= 1.0
+    final Double wrappedNoCFSRatio  = random().nextBoolean() ? null : random().nextInt(N+1)/((double)N); // must be: 0.0 <= value <= 1.0
+    implTestUpgradeIndexMergePolicyFactory(wrappingNoCFSRatio, wrappedNoCFSRatio);
+  }
+
+  private void implTestUpgradeIndexMergePolicyFactory(Double wrappingNoCFSRatio, Double wrappedNoCFSRatio) {
+    final MergePolicyFactoryArgs args = new MergePolicyFactoryArgs();
+    if (wrappingNoCFSRatio != null) {
+      args.add("noCFSRatio", wrappingNoCFSRatio); // noCFSRatio for the wrapping merge policy
+    }
+    args.add(WrapperMergePolicyFactory.WRAPPED_PREFIX, "wrapped");
+    args.add("wrapped.class", TieredMergePolicyFactory.class.getName());
+    if (wrappedNoCFSRatio != null) {
+      args.add("wrapped.noCFSRatio", wrappedNoCFSRatio); // noCFSRatio for the wrapped merge policy
+    }
+
+    MergePolicyFactory mpf;
+    try {
+      mpf = new UpgradeIndexMergePolicyFactory(resourceLoader, args, null);
+      assertFalse("Should only reach here if wrapping and wrapped args don't overlap!",
+          (wrappingNoCFSRatio != null && wrappedNoCFSRatio != null));
+
+      for (int ii=1; ii<=2; ++ii) { // it should be okay to call getMergePolicy() more than once
+        final MergePolicy mp = mpf.getMergePolicy();
+        if (wrappingNoCFSRatio != null) {
+          assertEquals("#"+ii+" wrappingNoCFSRatio", wrappingNoCFSRatio.doubleValue(), mp.getNoCFSRatio(), 0.0d);
+        }
+        if (wrappedNoCFSRatio != null) {
+          assertEquals("#"+ii+" wrappedNoCFSRatio", wrappedNoCFSRatio.doubleValue(), mp.getNoCFSRatio(), 0.0d);
+        }
+        assertSame(mp.getClass(), UpgradeIndexMergePolicy.class);
+      }
+
+    } catch (IllegalArgumentException iae) {
+      assertEquals("Wrapping and wrapped merge policy args overlap! [noCFSRatio]", iae.getMessage());
+      assertTrue("Should only reach here if wrapping and wrapped args do overlap!",
+          (wrappingNoCFSRatio != null && wrappedNoCFSRatio != null));
+    }
+  }
+
   private static class DefaultingWrapperMergePolicyFactory extends WrapperMergePolicyFactory {
 
     DefaultingWrapperMergePolicyFactory(SolrResourceLoader resourceLoader, MergePolicyFactoryArgs wrapperArgs, IndexSchema schema) {