diff --git a/lucene/facet/src/java/org/apache/lucene/facet/taxonomy/CategoryPath.java b/lucene/facet/src/java/org/apache/lucene/facet/taxonomy/CategoryPath.java
index 4e62926578f..33f7400c1bd 100644
--- a/lucene/facet/src/java/org/apache/lucene/facet/taxonomy/CategoryPath.java
+++ b/lucene/facet/src/java/org/apache/lucene/facet/taxonomy/CategoryPath.java
@@ -121,6 +121,14 @@ public class CategoryPath implements Comparable<CategoryPath> {
     return length - other.length;
   }
 
+  private void noDelimiter(char[] buf, int offset, int len, char delimiter) {
+    for(int idx=0;idx<len;idx++) {
+      if (buf[offset+idx] == delimiter) {
+        throw new IllegalArgumentException("delimiter character U+" + Integer.toHexString(delimiter) + " appears in path");
+      }
+    }
+  }
+
   /**
    * Copies the path components to the given {@code char[]}, starting at index
    * {@code start}. {@code delimiter} is copied between the path components.
@@ -141,10 +149,12 @@ public class CategoryPath implements Comparable<CategoryPath> {
     for (int i = 0; i < upto; i++) {
       int len = components[i].length();
       components[i].getChars(0, len, buf, idx);
+      noDelimiter(buf, idx, len, delimiter);
       idx += len;
       buf[idx++] = delimiter;
     }
     components[upto].getChars(0, components[upto].length(), buf, idx);
+    noDelimiter(buf, idx, components[upto].length(), delimiter);
     
     return idx + components[upto].length() - start;
   }
diff --git a/lucene/facet/src/test/org/apache/lucene/facet/search/TestDemoFacets.java b/lucene/facet/src/test/org/apache/lucene/facet/search/TestDemoFacets.java
index 34351a98024..e6e63e0217e 100644
--- a/lucene/facet/src/test/org/apache/lucene/facet/search/TestDemoFacets.java
+++ b/lucene/facet/src/test/org/apache/lucene/facet/search/TestDemoFacets.java
@@ -47,6 +47,7 @@ import org.apache.lucene.search.similarities.DefaultSimilarity;
 import org.apache.lucene.search.similarities.PerFieldSimilarityWrapper;
 import org.apache.lucene.search.similarities.Similarity;
 import org.apache.lucene.store.Directory;
+import org.apache.lucene.util.BytesRef;
 
 public class TestDemoFacets extends FacetTestCase {
 
@@ -219,4 +220,27 @@ public class TestDemoFacets extends FacetTestCase {
     dir.close();
     taxoDir.close();
   }
+
+  public void testLabelWithDelimiter() throws Exception {
+    Directory dir = newDirectory();
+    Directory taxoDir = newDirectory();
+    RandomIndexWriter writer = new RandomIndexWriter(random(), dir);
+    DirectoryTaxonomyWriter taxoWriter = new DirectoryTaxonomyWriter(taxoDir, IndexWriterConfig.OpenMode.CREATE);
+
+    FacetFields facetFields = new FacetFields(taxoWriter);
+
+    Document doc = new Document();
+    doc.add(newTextField("field", "text", Field.Store.NO));
+    BytesRef br = new BytesRef(new byte[] {(byte) 0xee, (byte) 0x92, (byte) 0xaa, (byte) 0xef, (byte) 0x9d, (byte) 0x89});
+    facetFields.addFields(doc, Collections.singletonList(new CategoryPath("dim/" + br.utf8ToString(), '/')));
+    try {
+      writer.addDocument(doc);
+    } catch (IllegalArgumentException iae) {
+      // expected
+    }
+    writer.close();
+    taxoWriter.close();
+    dir.close();
+    taxoDir.close();
+  }
 }
diff --git a/lucene/facet/src/test/org/apache/lucene/facet/search/TestDrillSideways.java b/lucene/facet/src/test/org/apache/lucene/facet/search/TestDrillSideways.java
index 927ce2ba094..adab34b1f9a 100644
--- a/lucene/facet/src/test/org/apache/lucene/facet/search/TestDrillSideways.java
+++ b/lucene/facet/src/test/org/apache/lucene/facet/search/TestDrillSideways.java
@@ -33,6 +33,7 @@ import org.apache.lucene.document.Field;
 import org.apache.lucene.document.StringField;
 import org.apache.lucene.facet.FacetTestCase;
 import org.apache.lucene.facet.index.FacetFields;
+import org.apache.lucene.facet.params.FacetIndexingParams;
 import org.apache.lucene.facet.params.FacetSearchParams;
 import org.apache.lucene.facet.search.DrillSideways.DrillSidewaysResult;
 import org.apache.lucene.facet.taxonomy.CategoryPath;
@@ -58,6 +59,7 @@ import org.apache.lucene.search.TermQuery;
 import org.apache.lucene.search.TopDocs;
 import org.apache.lucene.store.Directory;
 import org.apache.lucene.util.Bits;
+import org.apache.lucene.util.BytesRef;
 import org.apache.lucene.util.FixedBitSet;
 import org.apache.lucene.util.InfoStream;
 import org.apache.lucene.util._TestUtil;
@@ -374,7 +376,15 @@ public class TestDrillSideways extends FacetTestCase {
     for(int dim=0;dim<numDims;dim++) {
       Set<String> values = new HashSet<String>();
       while (values.size() < valueCount) {
-        String s = _TestUtil.randomRealisticUnicodeString(random());
+        String s;
+        while (true) {
+          s = _TestUtil.randomRealisticUnicodeString(random());
+          // We cannot include this character else the label
+          // is silently truncated:
+          if (s.indexOf(FacetIndexingParams.DEFAULT_FACET_DELIM_CHAR) == -1) {
+            break;
+          }
+        }
         //String s = _TestUtil.randomSimpleString(random());
         if (s.length() > 0) {
           values.add(s);
@@ -443,7 +453,7 @@ public class TestDrillSideways extends FacetTestCase {
           paths.add(new CategoryPath("dim" + dim, dimValues[dim][dimValue]));
           doc.add(new StringField("dim" + dim, dimValues[dim][dimValue], Field.Store.YES));
           if (VERBOSE) {
-            System.out.println("    dim" + dim + "=" + dimValues[dim][dimValue]);
+            System.out.println("    dim" + dim + "=" + new BytesRef(dimValues[dim][dimValue]));
           }
         }
         int dimValue2 = rawDoc.dims2[dim];
@@ -451,7 +461,7 @@ public class TestDrillSideways extends FacetTestCase {
           paths.add(new CategoryPath("dim" + dim, dimValues[dim][dimValue2]));
           doc.add(new StringField("dim" + dim, dimValues[dim][dimValue2], Field.Store.YES));
           if (VERBOSE) {
-            System.out.println("      dim" + dim + "=" + dimValues[dim][dimValue2]);
+            System.out.println("      dim" + dim + "=" + new BytesRef(dimValues[dim][dimValue2]));
           }
         }
       }
@@ -541,7 +551,11 @@ public class TestDrillSideways extends FacetTestCase {
             }
           }
           if (VERBOSE) {
-            System.out.println("  dim" + dim + "=" + Arrays.toString(drillDowns[dim]));
+            BytesRef[] values = new BytesRef[drillDowns[dim].length];
+            for(int i=0;i<values.length;i++) {
+              values[i] = new BytesRef(drillDowns[dim][i]);
+            }
+            System.out.println("  dim" + dim + "=" + Arrays.toString(values));
           }
           count++;
         }
@@ -792,7 +806,7 @@ public class TestDrillSideways extends FacetTestCase {
       for(FacetResultNode childNode : fr.getFacetResultNode().subResults) {
         actualValues.put(childNode.label.components[1], (int) childNode.value);
         if (VERBOSE) {
-          System.out.println("        " + childNode.label.components[1] + ": " + (int) childNode.value);
+          System.out.println("        " + new BytesRef(childNode.label.components[1]) + ": " + (int) childNode.value);
         }
       }
 
@@ -805,7 +819,7 @@ public class TestDrillSideways extends FacetTestCase {
         String value = dimValues[dim][i];
         if (expected.counts[dim][i] != 0) {
           if (VERBOSE) {
-            System.out.println("        " + value + ": " + expected.counts[dim][i]);
+            System.out.println("        " + new BytesRef(value) + ": " + expected.counts[dim][i]);
           } 
           assertTrue(actualValues.containsKey(value));
           assertEquals(expected.counts[dim][i], actualValues.get(value).intValue());