Index: oak-jcr/src/test/java/org/apache/jackrabbit/oak/jcr/ValidNamesTest.java
===================================================================
--- oak-jcr/src/test/java/org/apache/jackrabbit/oak/jcr/ValidNamesTest.java	(revision 1781053)
+++ oak-jcr/src/test/java/org/apache/jackrabbit/oak/jcr/ValidNamesTest.java	(working copy)
@@ -264,10 +264,8 @@
         nameTest("foo\u3000bar");
     }
 
-    @Test
+    @Test(expected = IllegalStateException.class)
     public void testUnpairedSurrogate() throws RepositoryException {
-        // see OAK-5506
-        org.junit.Assume.assumeFalse(super.fixture.toString().toLowerCase().contains("segment"));
         nameTest("foo\ud800");
     }
 
Index: oak-run/src/main/java/org/apache/jackrabbit/oak/benchmark/BenchmarkRunner.java
===================================================================
--- oak-run/src/main/java/org/apache/jackrabbit/oak/benchmark/BenchmarkRunner.java	(revision 1781053)
+++ oak-run/src/main/java/org/apache/jackrabbit/oak/benchmark/BenchmarkRunner.java	(working copy)
@@ -433,7 +433,8 @@
             new SyncExternalUsersTest(numberOfUsers.value(options), numberOfGroups.value(options), expiration.value(options), dynamicMembership.value(options), autoMembership.values(options), batchSize.value(options)),
             new HybridIndexTest(base.value(options), statsProvider),
             new BundlingNodeTest(),
-            new PersistentCacheTest(statsProvider)
+            new PersistentCacheTest(statsProvider),
+            new StringWriteTest()
         };
 
         Set<String> argset = Sets.newHashSet(nonOption.values(options));
Index: oak-run/src/main/java/org/apache/jackrabbit/oak/benchmark/StringWriteTest.java
===================================================================
--- oak-run/src/main/java/org/apache/jackrabbit/oak/benchmark/StringWriteTest.java	(nonexistent)
+++ oak-run/src/main/java/org/apache/jackrabbit/oak/benchmark/StringWriteTest.java	(working copy)
@@ -0,0 +1,63 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.jackrabbit.oak.benchmark;
+
+import java.util.UUID;
+
+import javax.jcr.Node;
+import javax.jcr.RepositoryException;
+import javax.jcr.Session;
+
+public class StringWriteTest extends AbstractTest {
+
+    private static final int PROPERTY_COUNT = Integer.getInteger("StringWriteTest.propertyCount", 100);
+
+    private static String randomString() {
+        return UUID.randomUUID().toString();
+    }
+
+    private Session session;
+
+    private Node root;
+
+    @Override
+    public void beforeSuite() throws RepositoryException {
+        session = loginWriter();
+    }
+
+    @Override
+    protected void beforeTest() throws Exception {
+        root = session.getRootNode().addNode("StringWrite" + TEST_ID, "nt:unstructured");
+        session.save();
+    }
+
+    @Override
+    protected void runTest() throws Exception {
+        for (int i = 0; i < PROPERTY_COUNT; i++) {
+            root.setProperty(randomString(), randomString());
+        }
+        session.save();
+    }
+
+    @Override
+    protected void afterTest() throws Exception {
+        root.remove();
+        session.save();
+    }
+
+}

Property changes on: oak-run/src/main/java/org/apache/jackrabbit/oak/benchmark/StringWriteTest.java
___________________________________________________________________
Added: svn:eol-style
## -0,0 +1 ##
+native
\ No newline at end of property
Index: oak-segment-tar/src/main/java/org/apache/jackrabbit/oak/segment/SegmentWriter.java
===================================================================
--- oak-segment-tar/src/main/java/org/apache/jackrabbit/oak/segment/SegmentWriter.java	(revision 1781053)
+++ oak-segment-tar/src/main/java/org/apache/jackrabbit/oak/segment/SegmentWriter.java	(working copy)
@@ -87,6 +87,24 @@
 
     static final int BLOCK_SIZE = 1 << 12; // 4kB
 
+    private static void checkValidString(String s) throws IOException {
+        for (int i = 0; i < s.length(); i++) {
+            char c1 = s.charAt(i);
+            if (Character.isSurrogate(c1)) {
+                try {
+                    char c2 = s.charAt(i + 1);
+                    if (Character.isSurrogatePair(c1, c2)) {
+                        i += 1;
+                    } else {
+                        throw new IOException("Invalid surrogate pair sequence: " + (int) c1 + " " + (int) c2);
+                    }
+                } catch (IndexOutOfBoundsException ex) {
+                    throw new IOException("String ends in unpaired surrogate character.", ex);
+                }
+            }
+        }
+    }
+
     @Nonnull
     private final WriterCacheManager cacheManager;
 
@@ -687,6 +705,8 @@
                 return id; // shortcut if the same string was recently stored
             }
 
+            checkValidString(string);
+
             byte[] data = string.getBytes(UTF_8);
 
             if (data.length < Segment.MEDIUM_LIMIT) {