diff --git a/Stack/Opc.Ua.Core/Types/Utils/RelativePath.cs b/Stack/Opc.Ua.Core/Types/Utils/RelativePath.cs
index 6c02f169de..cf1e55ad86 100644
--- a/Stack/Opc.Ua.Core/Types/Utils/RelativePath.cs
+++ b/Stack/Opc.Ua.Core/Types/Utils/RelativePath.cs
@@ -354,6 +354,12 @@ public void TranslateNamespaceIndexes(NamespaceTable currentTable, NamespaceTabl
                     {
                         element.ReferenceTypeName = new QualifiedName(qname.Name, (ushort)mappings[qname.NamespaceIndex]);
                     }
+                    else
+                    {
+                        throw new ServiceResultException(
+                            StatusCodes.BadIndexRangeInvalid,
+                            Utils.Format("Cannot translate namespace index '{0}' to target namespace table.", qname.NamespaceIndex));
+                    }
                 }
 
                 qname = element.TargetName;
@@ -364,6 +370,12 @@ public void TranslateNamespaceIndexes(NamespaceTable currentTable, NamespaceTabl
                     {
                         element.TargetName = new QualifiedName(qname.Name, (ushort)mappings[qname.NamespaceIndex]);
                     }
+                    else
+                    {
+                        throw new ServiceResultException(
+                            StatusCodes.BadIndexRangeInvalid,
+                            Utils.Format("Cannot translate namespace index '{0}' to target namespace table.", qname.NamespaceIndex));
+                    }
                 }
             }
         }
diff --git a/Tests/Opc.Ua.Core.Tests/Types/Utils/UtilsTests.cs b/Tests/Opc.Ua.Core.Tests/Types/Utils/UtilsTests.cs
index 0fd8f272a6..2ba538b993 100644
--- a/Tests/Opc.Ua.Core.Tests/Types/Utils/UtilsTests.cs
+++ b/Tests/Opc.Ua.Core.Tests/Types/Utils/UtilsTests.cs
@@ -298,6 +298,55 @@ public void RelativePathParseAlphanumericWithNamespaceIndexStringPath()
             Assert.AreEqual(str, RelativePath.Parse(str, typeTable).Format(typeTable));
         }
 
+        /// <summary>
+        /// Parse path string containing two Namespaces, translate indexes
+        /// </summary>
+        [Theory]
+        [TestCase("<#2:HasChild>", "<#3:HasChild>")]
+        [TestCase("<!2:HasChild>", "<!3:HasChild>")]
+        [TestCase(".2:NodeVersion", ".3:NodeVersion")]
+        [TestCase("/1:abc/2:def", "/1:abc/3:def")]
+        public void RelativePathParseTranslateNamespaceIndexReferenceType(string input, string output)
+        {
+            var currentTable = new NamespaceTable(new List<string>() { Namespaces.OpcUa, "1", Namespaces.OpcUaGds });
+            var targetTable = new NamespaceTable(new List<string>() { Namespaces.OpcUa, "1", "2", Namespaces.OpcUaGds });
+
+            TypeTable typeTable = new TypeTable(new NamespaceTable());
+            typeTable.AddReferenceSubtype(Opc.Ua.ReferenceTypeIds.HasChild, NodeId.Null, new QualifiedName("HasChild", 3));
+            Assert.AreEqual(output, RelativePath.Parse(input, typeTable, currentTable, targetTable).Format(typeTable));
+        }
+
+
+        /// <summary>
+        /// Parse path string containing two Namespaces with missing namespace indexes in either currentTable or targetTable.
+        /// </summary>
+        [Theory]
+        [TestCase(
+            new string[] { Namespaces.OpcUa, "2", Namespaces.OpcUaGds },
+            new string[] { Namespaces.OpcUa, "2", "3" },
+            "/1:abc/2:def"
+        )]
+        [TestCase(
+            new string[] { Namespaces.OpcUa, "2", Namespaces.OpcUaGds },
+            new string[] { Namespaces.OpcUa, "2", "3" },
+            "<#2:HasChild>"
+        )]
+        [TestCase(
+            new string[] { Namespaces.OpcUa, "2", Namespaces.OpcUaGds },
+            new string[] { Namespaces.OpcUa, "2", "3", "4", "5" },
+            "/1:abc/4:def"
+        )]
+        public void RelativePathParseInvalidNamespaceIndex(string[] currentNamespaces, string[] targetNamespaces, string path)
+        {
+            var currentTable = new NamespaceTable(new List<string>(currentNamespaces));
+            var targetTable = new NamespaceTable(new List<string>(targetNamespaces));
+
+            TypeTable typeTable = new TypeTable(new NamespaceTable());
+            var sre = Assert.Throws<ServiceResultException>(() => RelativePath.Parse(path, typeTable, currentTable, targetTable).Format(typeTable));
+            Assert.AreEqual((StatusCode)StatusCodes.BadIndexRangeInvalid, (StatusCode)sre.StatusCode);
+        }
+
+
         /// <summary>
         /// Validate that XmlDocument DtdProcessing is protected against
         /// exponential entity expansion in this version of .NET.