diff --git a/lucene/core/src/java/org/apache/lucene/util/hash/HashFunction.java b/lucene/core/src/java/org/apache/lucene/util/hash/HashFunction.java
index fdb7b013345..1d940ad3734 100644
--- a/lucene/core/src/java/org/apache/lucene/util/hash/HashFunction.java
+++ b/lucene/core/src/java/org/apache/lucene/util/hash/HashFunction.java
@@ -62,7 +62,21 @@ public abstract class HashFunction implements NamedSPILoader.NamedSPI {
     return loader.availableServices();
   }
   
-
+  /** 
+   * Reloads the hash function list from the given {@link ClassLoader}.
+   * Changes to the function list are visible after the method ends, all
+   * iterators ({@link #availableHashFunctionNames()},...) stay consistent. 
+   * 
+   * <p><b>NOTE:</b> Only new functions are added, existing ones are
+   * never removed or replaced.
+   * 
+   * <p><em>This method is expensive and should only be called for discovery
+   * of new functions on the given classpath/classloader!</em>
+   */
+  public static void reloadHashFunctions(ClassLoader classloader) {
+    loader.reload(classloader);
+  }
+  
   @Override
   public String toString() {
     return name;
diff --git a/solr/core/src/java/org/apache/solr/core/SolrResourceLoader.java b/solr/core/src/java/org/apache/solr/core/SolrResourceLoader.java
index 8180d411f97..d7825b8fd39 100644
--- a/solr/core/src/java/org/apache/solr/core/SolrResourceLoader.java
+++ b/solr/core/src/java/org/apache/solr/core/SolrResourceLoader.java
@@ -36,6 +36,7 @@ import org.apache.lucene.analysis.util.TokenFilterFactory;
 import org.apache.lucene.analysis.util.TokenizerFactory;
 import org.apache.lucene.codecs.Codec;
 import org.apache.lucene.codecs.PostingsFormat;
+import org.apache.lucene.util.hash.HashFunction;
 import org.apache.lucene.analysis.util.WordlistLoader;
 import org.apache.solr.common.ResourceLoader;
 import org.apache.solr.handler.admin.CoreAdminHandler;
@@ -175,6 +176,8 @@ public class SolrResourceLoader implements ResourceLoader
    * this ResourceLoader.
    */
   void reloadLuceneSPI() {
+    // Hash functions:
+    HashFunction.reloadHashFunctions(this.classLoader);
     // Codecs:
     PostingsFormat.reloadPostingsFormats(this.classLoader);
     Codec.reloadCodecs(this.classLoader);