diff --git a/jackrabbit-spi-commons/src/main/java/org/apache/jackrabbit/spi/commons/namespace/SessionNamespaceResolver.java b/jackrabbit-spi-commons/src/main/java/org/apache/jackrabbit/spi/commons/namespace/SessionNamespaceResolver.java
index 4d13fab49e4..528d033743d 100644
--- a/jackrabbit-spi-commons/src/main/java/org/apache/jackrabbit/spi/commons/namespace/SessionNamespaceResolver.java
+++ b/jackrabbit-spi-commons/src/main/java/org/apache/jackrabbit/spi/commons/namespace/SessionNamespaceResolver.java
@@ -47,7 +47,7 @@ public String getPrefix(String uri) throws NamespaceException {
             return session.getNamespacePrefix(uri);
         } catch (RepositoryException e) {
             // should never get here...
-            throw new NamespaceException("internal error: failed to resolve namespace uri", e);
+            throw new NamespaceException("internal error: failed to resolve namespace uri: '" + uri + "'", e);
         }
     }
 
@@ -59,7 +59,7 @@ public String getURI(String prefix) throws NamespaceException {
             return session.getNamespaceURI(prefix);
         } catch (RepositoryException e) {
             // should never get here...
-            throw new NamespaceException("internal error: failed to resolve namespace prefix", e);
+            throw new NamespaceException("internal error: failed to resolve namespace prefix: '" + prefix + "'", e);
         }
     }
 }