diff --git a/oak-jcr/src/main/java/org/apache/jackrabbit/oak/jcr/session/SessionImpl.java b/oak-jcr/src/main/java/org/apache/jackrabbit/oak/jcr/session/SessionImpl.java
index 3e46354..c8407f1 100644
--- a/oak-jcr/src/main/java/org/apache/jackrabbit/oak/jcr/session/SessionImpl.java
+++ b/oak-jcr/src/main/java/org/apache/jackrabbit/oak/jcr/session/SessionImpl.java
@@ -444,6 +444,9 @@ public class SessionImpl implements JackrabbitSession {
                 return true;
             }
         });
+
+        // TODO keep namespace refresh either here or in ReadWriteNamespaceRegistry.refresh
+        sessionContext.getNamespaces().refresh();
     }
 
     @Override
diff --git a/oak-jcr/src/main/java/org/apache/jackrabbit/oak/jcr/session/SessionNamespaces.java b/oak-jcr/src/main/java/org/apache/jackrabbit/oak/jcr/session/SessionNamespaces.java
index e091a7f..e5f8acd 100644
--- a/oak-jcr/src/main/java/org/apache/jackrabbit/oak/jcr/session/SessionNamespaces.java
+++ b/oak-jcr/src/main/java/org/apache/jackrabbit/oak/jcr/session/SessionNamespaces.java
@@ -53,6 +53,9 @@ class SessionNamespaces extends LocalNameMapper {
     // The code below was initially copied from JCR Commons AbstractSession,
     // but has since been radically modified
 
+    // TODO is it safe to assume that the super class will never modify the local map? Otherwise we need some kind of event listeners
+    private String[] namespacePrefixesCache = null;
+
     /**
      * @see Session#setNamespacePrefix(String, String)
      */
@@ -90,12 +93,22 @@ class SessionNamespaces extends LocalNameMapper {
 
         // add the new mapping
         local.put(prefix, uri);
+
+        refresh();
     }
 
     /**
      * @see Session#getNamespacePrefixes()
      */
     synchronized String[] getNamespacePrefixes() {
+        if (namespacePrefixesCache == null) {
+            namespacePrefixesCache = internalGetNamespacePrefixes();
+        }
+        // Clone to avoid that the consumer can manipulate the cache
+        return namespacePrefixesCache.clone();
+    }
+
+    private String[] internalGetNamespacePrefixes() {
         // get registered namespace prefixes
         Iterable<String> global = emptyList();
         PropertyState property = nsdata.getProperty(REP_PREFIXES);
@@ -169,6 +182,7 @@ class SessionNamespaces extends LocalNameMapper {
         }
         if (base != prefix) {
             local.put(prefix, uri);
+            refresh();
         }
 
         return prefix;
@@ -179,6 +193,14 @@ class SessionNamespaces extends LocalNameMapper {
      */
     synchronized void clear() {
         local.clear();
+        refresh();
+    }
+
+    /**
+     * Clears the namespace prefixes cache.
+     */
+    synchronized void refresh() {
+        namespacePrefixesCache = null;
     }
 
 }
diff --git a/oak-jcr/src/main/java/org/apache/jackrabbit/oak/jcr/session/WorkspaceImpl.java b/oak-jcr/src/main/java/org/apache/jackrabbit/oak/jcr/session/WorkspaceImpl.java
index 4e0e6fc..94bc4f9 100644
--- a/oak-jcr/src/main/java/org/apache/jackrabbit/oak/jcr/session/WorkspaceImpl.java
+++ b/oak-jcr/src/main/java/org/apache/jackrabbit/oak/jcr/session/WorkspaceImpl.java
@@ -219,6 +219,8 @@ public class WorkspaceImpl implements JackrabbitWorkspace {
             @Override
             protected void refresh() throws RepositoryException {
                 getSession().refresh(true);
+                // TODO keep namespace refresh either here or in SessionImpl.refresh
+                sessionContext.getNamespaces().refresh();
             }
         };
     }