diff --git a/lib/csharp/src/Protocol/TProtocolUtil.cs b/lib/csharp/src/Protocol/TProtocolUtil.cs
index 0932a7f..0606c71 100644
--- a/lib/csharp/src/Protocol/TProtocolUtil.cs
+++ b/lib/csharp/src/Protocol/TProtocolUtil.cs
@@ -95,6 +95,8 @@
                         }
                         prot.ReadListEnd();
                         break;
+                    default:
+                        throw new TProtocolException(TProtocolException.INVALID_DATA, "Unknown data type " + type.ToString("d"));
                 }
 
             }
diff --git a/lib/delphi/src/Thrift.Protocol.pas b/lib/delphi/src/Thrift.Protocol.pas
index 7ff2eae..9ea28de 100644
--- a/lib/delphi/src/Thrift.Protocol.pas
+++ b/lib/delphi/src/Thrift.Protocol.pas
@@ -823,7 +823,7 @@
     end;
 
   else
-    ASSERT( FALSE); // any new types?
+    raise TProtocolExceptionInvalidData.Create('Unexpected type '+IntToStr(Ord(type_)));
   end;
 end;
 
diff --git a/lib/go/thrift/protocol.go b/lib/go/thrift/protocol.go
index 45fa202..32bb7b3 100644
--- a/lib/go/thrift/protocol.go
+++ b/lib/go/thrift/protocol.go
@@ -21,6 +21,7 @@
 
 import (
 	"errors"
+	"fmt"
 )
 
 const (
@@ -170,6 +171,8 @@
 			}
 		}
 		return self.ReadListEnd()
+	default:
+		return NewTProtocolExceptionWithType(INVALID_DATA, errors.New(fmt.Sprintf("Unknown data type %d", fieldType)))
 	}
 	return nil
 }
diff --git a/lib/haxe/src/org/apache/thrift/protocol/TProtocolUtil.hx b/lib/haxe/src/org/apache/thrift/protocol/TProtocolUtil.hx
index 1ec59d2..001e405 100644
--- a/lib/haxe/src/org/apache/thrift/protocol/TProtocolUtil.hx
+++ b/lib/haxe/src/org/apache/thrift/protocol/TProtocolUtil.hx
@@ -95,7 +95,7 @@
                     prot.readListEnd();
 
                 default:
-                    trace("Unknown field type ",type," in skipMaxDepth()");
+					throw new TProtocolException(TProtocolException.UNKNOWN, "Unknown field type ${type}");
             }
 
             prot.DecrementRecursionDepth();
diff --git a/lib/netcore/Thrift/Protocols/Utilities/TProtocolUtil.cs b/lib/netcore/Thrift/Protocols/Utilities/TProtocolUtil.cs
index 6232149..038edb9 100644
--- a/lib/netcore/Thrift/Protocols/Utilities/TProtocolUtil.cs
+++ b/lib/netcore/Thrift/Protocols/Utilities/TProtocolUtil.cs
@@ -97,6 +97,8 @@
                         }
                         await prot.ReadListEndAsync(cancellationToken);
                         break;
+                    default:
+                        throw new TProtocolException(TProtocolException.INVALID_DATA, "Unknown data type " + type.ToString("d"));
                 }
             }
             finally