diff --git a/solr/CHANGES.txt b/solr/CHANGES.txt
index 33490d62ab7..b430eb645f4 100644
--- a/solr/CHANGES.txt
+++ b/solr/CHANGES.txt
@@ -363,6 +363,9 @@ Bug Fixes
 * SOLR-2763: Extracting update request handler throws exception and returns 400 
   when zero-length file posted using multipart form post (janhoy)
 
+* SOLR-2780: Fixed issue where multi select facets didn't respect group.truncate parameter.
+  (Martijn van Groningen, Ramzi Alqrainy)
+
  Other Changes
 ----------------------
 
diff --git a/solr/core/src/java/org/apache/solr/request/SimpleFacets.java b/solr/core/src/java/org/apache/solr/request/SimpleFacets.java
index d6cedaaada3..a99767b477a 100644
--- a/solr/core/src/java/org/apache/solr/request/SimpleFacets.java
+++ b/solr/core/src/java/org/apache/solr/request/SimpleFacets.java
@@ -18,11 +18,14 @@
 package org.apache.solr.request;
 
 import org.apache.lucene.index.*;
+import org.apache.lucene.queries.function.FunctionQuery;
+import org.apache.lucene.queries.function.ValueSource;
+import org.apache.lucene.queries.function.valuesource.QueryValueSource;
 import org.apache.lucene.queryparser.classic.ParseException;
 import org.apache.lucene.search.*;
-import org.apache.lucene.util.BytesRef;
-import org.apache.lucene.util.CharsRef;
-import org.apache.lucene.util.UnicodeUtil;
+import org.apache.lucene.search.grouping.AbstractAllGroupHeadsCollector;
+import org.apache.lucene.search.grouping.TermAllGroupHeadsCollector;
+import org.apache.lucene.util.*;
 import org.apache.lucene.util.packed.Direct16;
 import org.apache.lucene.util.packed.Direct32;
 import org.apache.lucene.util.packed.Direct8;
@@ -162,7 +165,26 @@ public class SimpleFacets {
       }
 
       // get the new base docset for this facet
-      base = searcher.getDocSet(qlist);
+      DocSet base = searcher.getDocSet(qlist);
+      if (rb.grouping() && rb.getGroupingSpec().isTruncateGroups()) {
+        Grouping grouping = new Grouping(searcher, null, rb.getQueryCommand(), false, 0, false);
+        if (rb.getGroupingSpec().getFields().length > 0) {
+          grouping.addFieldCommand(rb.getGroupingSpec().getFields()[0], req);
+        } else if (rb.getGroupingSpec().getFunctions().length > 0) {
+          grouping.addFunctionCommand(rb.getGroupingSpec().getFunctions()[0], req);
+        } else {
+          this.base = base;
+          return;
+        }
+        AbstractAllGroupHeadsCollector allGroupHeadsCollector = grouping.getCommands().get(0).createAllGroupCollector();
+        searcher.search(new MatchAllDocsQuery(), base.getTopFilter(), allGroupHeadsCollector);
+        int maxDoc = searcher.maxDoc();
+        FixedBitSet fixedBitSet = allGroupHeadsCollector.retrieveGroupHeads(maxDoc);
+        long[] bits = fixedBitSet.getBits();
+        this.base = new BitDocSet(new OpenBitSet(bits, bits.length));
+      } else {
+        this.base = base;
+      }
     }
 
   }
diff --git a/solr/core/src/test/org/apache/solr/TestGroupingSearch.java b/solr/core/src/test/org/apache/solr/TestGroupingSearch.java
index ea3451b91eb..0951e36a239 100644
--- a/solr/core/src/test/org/apache/solr/TestGroupingSearch.java
+++ b/solr/core/src/test/org/apache/solr/TestGroupingSearch.java
@@ -279,6 +279,33 @@ public class TestGroupingSearch extends SolrTestCaseJ4 {
         "/grouped=={'value4_i':{'matches':5,'groups':[{'groupValue':1,'doclist':{'numFound':3,'start':0,'docs':[{'id':'1'}]}}]}}",
         "/facet_counts=={'facet_queries':{},'facet_fields':{'value3_s1':['a',1,'b',1]},'facet_dates':{},'facet_ranges':{}}"
     );
+
+    // Multi select facets AND group.truncate=true
+    req = req("q", "*:*", "rows", "1", "group", "true", "group.field", "value4_i", "fl", "id", "facet", "true",
+        "facet.field", "{!ex=v}value3_s1", "group.truncate", "true", "fq", "{!tag=v}value3_s1:b");
+    assertJQ(
+        req,
+        "/grouped=={'value4_i':{'matches':2,'groups':[{'groupValue':2,'doclist':{'numFound':2,'start':0,'docs':[{'id':'3'}]}}]}}",
+        "/facet_counts=={'facet_queries':{},'facet_fields':{'value3_s1':['a',1,'b',1]},'facet_dates':{},'facet_ranges':{}}"
+    );
+
+    // Multi select facets AND group.truncate=false
+    req = req("q", "*:*", "rows", "1", "group", "true", "group.field", "value4_i", "fl", "id", "facet", "true",
+        "facet.field", "{!ex=v}value3_s1", "group.truncate", "false", "fq", "{!tag=v}value3_s1:b");
+    assertJQ(
+        req,
+        "/grouped=={'value4_i':{'matches':2,'groups':[{'groupValue':2,'doclist':{'numFound':2,'start':0,'docs':[{'id':'3'}]}}]}}",
+        "/facet_counts=={'facet_queries':{},'facet_fields':{'value3_s1':['a',3,'b',2]},'facet_dates':{},'facet_ranges':{}}"
+    );
+
+    // Multi select facets AND group.truncate=true
+    req = req("q", "*:*", "rows", "1", "group", "true", "group.func", "sub(value4_i,1)", "fl", "id", "facet", "true",
+        "facet.field", "{!ex=v}value3_s1", "group.truncate", "true", "fq", "{!tag=v}value3_s1:b");
+    assertJQ(
+        req,
+        "/grouped=={'sub(value4_i,1)':{'matches':2,'groups':[{'groupValue':1.0,'doclist':{'numFound':2,'start':0,'docs':[{'id':'3'}]}}]}}",
+        "/facet_counts=={'facet_queries':{},'facet_fields':{'value3_s1':['a',1,'b',1]},'facet_dates':{},'facet_ranges':{}}"
+    );
   }
 
   static String f = "foo_i";