diff --git a/framework/src/main/java/org/apache/felix/framework/util/manifestparser/R4LibraryClause.java b/framework/src/main/java/org/apache/felix/framework/util/manifestparser/R4LibraryClause.java
index 0299041..162cbec 100644
--- a/framework/src/main/java/org/apache/felix/framework/util/manifestparser/R4LibraryClause.java
+++ b/framework/src/main/java/org/apache/felix/framework/util/manifestparser/R4LibraryClause.java
@@ -18,15 +18,93 @@
  */
 package org.apache.felix.framework.util.manifestparser;
 
-import java.util.*;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Dictionary;
+import java.util.HashMap;
+import java.util.Hashtable;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+import java.util.StringTokenizer;
 
 import org.apache.felix.framework.Logger;
 import org.apache.felix.framework.util.FelixConstants;
 import org.apache.felix.framework.util.VersionRange;
-import org.osgi.framework.*;
+import org.osgi.framework.BundleException;
+import org.osgi.framework.Constants;
+import org.osgi.framework.Filter;
+import org.osgi.framework.FrameworkUtil;
+import org.osgi.framework.Version;
 
 public class R4LibraryClause
 {
+    private static final String OS_AIX = "aix";
+    private static final String OS_DIGITALUNIX = "digitalunix";
+    private static final String OS_HPUX = "hpux";
+    private static final String OS_IRIX = "irix";
+    private static final String OS_LINUX = "linux";
+    private static final String OS_MACOS = "macos";
+    private static final String OS_NETBSD = "netbsd";
+    private static final String OS_NETWARE = "netware";
+    private static final String OS_OPENBSD = "openbsd";
+    private static final String OS_OS2 = "os2";
+    private static final String OS_QNX = "qnx";
+    private static final String OS_SOLARIS = "solaris";
+    private static final String OS_SUNOS = "sunos";
+    private static final String OS_VXWORKS = "vxworks";
+    private static final String OS_WINDOWS_2000 = "windows2000";
+    private static final String OS_WINDOWS_2003 = "windows2003";
+    private static final String OS_WINDOWS_7 = "windows7";
+    private static final String OS_WINDOWS_8 = "windows8";
+    private static final String OS_WINDOWS_9 = "windows9";
+    private static final String OS_WINDOWS_95 = "windows95";
+    private static final String OS_WINDOWS_98 = "windows98";
+    private static final String OS_WINDOWS_CE = "windowsce";
+    private static final String OS_WINDOWS_NT = "windowsnt";
+    private static final String OS_WINDOWS_SERVER_2008 = "windowsserver2008";
+    private static final String OS_WINDOWS_SERVER_2012 = "windowsserver2012";
+    private static final String OS_WINDOWS_VISTA = "windowsvista";
+    private static final String OS_WINDOWS_XP = "windowsxp";
+    private static final String OS_WIN_32 = "win32";
+
+    /* Storing the OS names in a map as this is quicker to look up.
+     */
+    private static final Map<String, String> NORMALIZED_OS_NAMES;
+    static {
+        Map<String, String> m = new HashMap<String, String>();
+        m.put(OS_AIX, "");
+        m.put(OS_DIGITALUNIX, "");
+        m.put(OS_HPUX, "");
+        m.put(OS_IRIX, "");
+        m.put(OS_LINUX, "");
+        m.put(OS_MACOS, "");
+        m.put(OS_NETBSD, "");
+        m.put(OS_NETWARE, "");
+        m.put(OS_OPENBSD, "");
+        m.put(OS_OS2, "");
+        m.put(OS_QNX, "");
+        m.put(OS_SOLARIS, "");
+        m.put(OS_SUNOS, "");
+        m.put(OS_VXWORKS, "");
+        m.put(OS_WINDOWS_2000, "");
+        m.put(OS_WINDOWS_2003, "");
+        m.put(OS_WINDOWS_7, "");
+        m.put(OS_WINDOWS_8, "");
+        m.put(OS_WINDOWS_9, "");
+        m.put(OS_WINDOWS_95, "");
+        m.put(OS_WINDOWS_98, "");
+        m.put(OS_WINDOWS_CE, "");
+        m.put(OS_WINDOWS_NT, "");
+        m.put(OS_WINDOWS_SERVER_2008, "");
+        m.put(OS_WINDOWS_SERVER_2012, "");
+        m.put(OS_WINDOWS_VISTA, "");
+        m.put(OS_WINDOWS_XP, "");
+        m.put(OS_WIN_32, "");
+
+        NORMALIZED_OS_NAMES = Collections.unmodifiableMap(m);
+    }
+
     private final String[] m_libraryEntries;
     private final String[] m_osnames;
     private final String[] m_processors;
@@ -134,12 +212,12 @@
 
     private boolean checkOSNames(String currentOSName, String[] osnames)
     {
-        boolean win32 = currentOSName.startsWith("win") && !currentOSName.equals("windowsce");
+        boolean win32 = currentOSName.startsWith("win") && !currentOSName.equals(OS_WINDOWS_CE);
 
         for (int i = 0; (osnames != null) && (i < osnames.length); i++)
         {
             if (osnames[i].equals(currentOSName) ||
-                ("win32".equals(osnames[i]) && win32))
+                (OS_WIN_32.equals(osnames[i]) && win32))
             {
                 return true;
             }
@@ -340,6 +418,12 @@
 
     public static String normalizeOSName(String value)
     {
+        if (NORMALIZED_OS_NAMES.containsKey(value))
+        {
+            // Already normalized
+            return value;
+        }
+
         value = value.toLowerCase();
 
         if (value.startsWith("win"))
@@ -347,117 +431,117 @@
             String os = "win";
             if (value.indexOf("32") >= 0 || value.indexOf("*") >= 0)
             {
-                os = "win32";
+                os = OS_WIN_32;
             }
             else if (value.indexOf("95") >= 0)
             {
-                os = "windows95";
+                os = OS_WINDOWS_95;
             }
             else if (value.indexOf("98") >= 0)
             {
-                os = "windows98";
+                os = OS_WINDOWS_98;
             }
             else if (value.indexOf("nt") >= 0)
             {
-                os = "windowsnt";
+                os = OS_WINDOWS_NT;
             }
             else if (value.indexOf("2000") >= 0)
             {
-                os = "windows2000";
+                os = OS_WINDOWS_2000;
             }
             else if (value.indexOf("2003") >= 0)
             {
-                os = "windows2003";
+                os = OS_WINDOWS_2003;
             }
             else if (value.indexOf("2008") >= 0)
             {
-                os = "windowsserver2008";
+                os = OS_WINDOWS_SERVER_2008;
             }
             else if (value.indexOf("2012") >= 0)
             {
-                os = "windowsserver2012";
+                os = OS_WINDOWS_SERVER_2012;
             }
             else if (value.indexOf("xp") >= 0)
             {
-                os = "windowsxp";
+                os = OS_WINDOWS_XP;
             }
             else if (value.indexOf("ce") >= 0)
             {
-                os = "windowsce";
+                os = OS_WINDOWS_CE;
             }
             else if (value.indexOf("vista") >= 0)
             {
-                os = "windowsvista";
+                os = OS_WINDOWS_VISTA;
             }
             else if ((value.indexOf(" 7") >= 0) || value.equals("win7"))
             {
-                os = "windows7";
+                os = OS_WINDOWS_7;
             }
             else if ((value.indexOf(" 8") >= 0) || value.equals("win8"))
             {
-                os = "windows8";
+                os = OS_WINDOWS_8;
             }
             else if ((value.indexOf(" 9") >= 0) || value.equals("win9"))
             {
-                os = "windows9";
+                os = OS_WINDOWS_9;
             }
             return os;
         }
-        else if (value.startsWith("linux"))
+        else if (value.startsWith(OS_LINUX))
         {
-            return "linux";
+            return OS_LINUX;
         }
-        else if (value.startsWith("aix"))
+        else if (value.startsWith(OS_AIX))
         {
-            return "aix";
+            return OS_AIX;
         }
-        else if (value.startsWith("digitalunix"))
+        else if (value.startsWith(OS_DIGITALUNIX))
         {
-            return "digitalunix";
+            return OS_DIGITALUNIX;
         }
-        else if (value.startsWith("hpux"))
+        else if (value.startsWith(OS_HPUX))
         {
-            return "hpux";
+            return OS_HPUX;
         }
-        else if (value.startsWith("irix"))
+        else if (value.startsWith(OS_IRIX))
         {
-            return "irix";
+            return OS_IRIX;
         }
-        else if (value.startsWith("macos") || value.startsWith("mac os"))
+        else if (value.startsWith(OS_MACOS) || value.startsWith("mac os"))
         {
-            return "macos";
+            return OS_MACOS;
         }
-        else if (value.startsWith("netware"))
+        else if (value.startsWith(OS_NETWARE))
         {
-            return "netware";
+            return OS_NETWARE;
         }
-        else if (value.startsWith("openbsd"))
+        else if (value.startsWith(OS_OPENBSD))
         {
-            return "openbsd";
+            return OS_OPENBSD;
         }
-        else if (value.startsWith("netbsd"))
+        else if (value.startsWith(OS_NETBSD))
         {
-            return "netbsd";
+            return OS_NETBSD;
         }
-        else if (value.startsWith("os2") || value.startsWith("os/2"))
+        else if (value.startsWith(OS_OS2) || value.startsWith("os/2"))
         {
-            return "os2";
+            return OS_OS2;
         }
-        else if (value.startsWith("qnx") || value.startsWith("procnto"))
+        else if (value.startsWith(OS_QNX) || value.startsWith("procnto"))
         {
-            return "qnx";
+            return OS_QNX;
         }
-        else if (value.startsWith("solaris"))
+        else if (value.startsWith(OS_SOLARIS))
         {
-            return "solaris";
+            return OS_SOLARIS;
         }
-        else if (value.startsWith("sunos"))
+        else if (value.startsWith(OS_SUNOS))
         {
-            return "sunos";
+            return OS_SUNOS;
         }
-        else if (value.startsWith("vxworks"))
+        else if (value.startsWith(OS_VXWORKS))
         {
-            return "vxworks";
+            return OS_VXWORKS;
         }
         return value;
     }
diff --git a/framework/src/test/java/org/apache/felix/framework/util/manifestparser/R4LibraryClauseTest.java b/framework/src/test/java/org/apache/felix/framework/util/manifestparser/R4LibraryClauseTest.java
new file mode 100644
index 0000000..b5effd2
--- /dev/null
+++ b/framework/src/test/java/org/apache/felix/framework/util/manifestparser/R4LibraryClauseTest.java
@@ -0,0 +1,84 @@
+/*
+ * 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.felix.framework.util.manifestparser;
+
+import junit.framework.TestCase;
+
+public class R4LibraryClauseTest extends TestCase {
+    public void testNormalizeOSName() {
+        assertEquals("win32", R4LibraryClause.normalizeOSName("win 32"));
+        assertEquals("win32", R4LibraryClause.normalizeOSName("Win*"));
+        assertEquals("windows95", R4LibraryClause.normalizeOSName("Windows 95"));
+        assertEquals("windows98", R4LibraryClause.normalizeOSName("Windows 98"));
+        assertEquals("windowsnt", R4LibraryClause.normalizeOSName("WinNT"));
+        assertEquals("windows2000", R4LibraryClause.normalizeOSName("Win2000"));
+        assertEquals("windows2003", R4LibraryClause.normalizeOSName("Win2003"));
+        assertEquals("windowsserver2008", R4LibraryClause.normalizeOSName("Windows Server 2008"));
+        assertEquals("windowsserver2012", R4LibraryClause.normalizeOSName("Windows Server 2012"));
+        assertEquals("windowsxp", R4LibraryClause.normalizeOSName("WinXP"));
+        assertEquals("windowsce", R4LibraryClause.normalizeOSName("WinCE"));
+        assertEquals("windowsvista", R4LibraryClause.normalizeOSName("WinVista"));
+        assertEquals("windows7", R4LibraryClause.normalizeOSName("Windows 7"));
+        assertEquals("windows8", R4LibraryClause.normalizeOSName("Win8"));
+        assertEquals("linux", R4LibraryClause.normalizeOSName("Linux1.2.3"));
+        assertEquals("aix", R4LibraryClause.normalizeOSName("AIX-4.5.6"));
+        assertEquals("digitalunix", R4LibraryClause.normalizeOSName("digitalunix_blah"));
+        assertEquals("hpux", R4LibraryClause.normalizeOSName("HPUX-999"));
+        assertEquals("irix", R4LibraryClause.normalizeOSName("Irixxxx"));
+        assertEquals("macos", R4LibraryClause.normalizeOSName("mac OS X"));
+        assertEquals("netware", R4LibraryClause.normalizeOSName("Netware"));
+        assertEquals("openbsd", R4LibraryClause.normalizeOSName("OpenBSD-0000"));
+        assertEquals("netbsd", R4LibraryClause.normalizeOSName("netbsd "));
+        assertEquals("os2", R4LibraryClause.normalizeOSName("os/2"));
+        assertEquals("qnx", R4LibraryClause.normalizeOSName("procnto"));
+        assertEquals("solaris", R4LibraryClause.normalizeOSName("Solaris 9"));
+        assertEquals("sunos", R4LibraryClause.normalizeOSName("SunOS8"));
+        assertEquals("vxworks", R4LibraryClause.normalizeOSName("VxWorks"));
+
+        // Try all the already normalized names
+        assertEquals("aix", R4LibraryClause.normalizeOSName("aix"));
+        assertEquals("digitalunix", R4LibraryClause.normalizeOSName("digitalunix"));
+        assertEquals("hpux", R4LibraryClause.normalizeOSName("hpux"));
+        assertEquals("irix", R4LibraryClause.normalizeOSName("irix"));
+        assertEquals("linux", R4LibraryClause.normalizeOSName("linux"));
+        assertEquals("macos", R4LibraryClause.normalizeOSName("macos"));
+        assertEquals("netbsd", R4LibraryClause.normalizeOSName("netbsd"));
+        assertEquals("netware", R4LibraryClause.normalizeOSName("netware"));
+        assertEquals("openbsd", R4LibraryClause.normalizeOSName("openbsd"));
+        assertEquals("os2", R4LibraryClause.normalizeOSName("os2"));
+        assertEquals("qnx", R4LibraryClause.normalizeOSName("qnx"));
+        assertEquals("solaris", R4LibraryClause.normalizeOSName("solaris"));
+        assertEquals("sunos", R4LibraryClause.normalizeOSName("sunos"));
+        assertEquals("vxworks", R4LibraryClause.normalizeOSName("vxworks"));
+        assertEquals("windows2000", R4LibraryClause.normalizeOSName("windows2000"));
+        assertEquals("windows2003", R4LibraryClause.normalizeOSName("windows2003"));
+        assertEquals("windows7", R4LibraryClause.normalizeOSName("windows7"));
+        assertEquals("windows8", R4LibraryClause.normalizeOSName("windows8"));
+        assertEquals("windows9", R4LibraryClause.normalizeOSName("windows9"));
+        assertEquals("windows95", R4LibraryClause.normalizeOSName("windows95"));
+        assertEquals("windows98", R4LibraryClause.normalizeOSName("windows98"));
+        assertEquals("windowsce", R4LibraryClause.normalizeOSName("windowsce"));
+        assertEquals("windowsnt", R4LibraryClause.normalizeOSName("windowsnt"));
+        assertEquals("windowsserver2008", R4LibraryClause.normalizeOSName("windowsserver2008"));
+        assertEquals("windowsserver2012", R4LibraryClause.normalizeOSName("windowsserver2012"));
+        assertEquals("windowsvista", R4LibraryClause.normalizeOSName("windowsvista"));
+        assertEquals("windowsxp", R4LibraryClause.normalizeOSName("windowsxp"));
+        assertEquals("win32", R4LibraryClause.normalizeOSName("win32"));
+    }
+}