--- a/main/trunk/interpreter/execution/RexxNativeActivation.cpp
+++ b/main/trunk/interpreter/execution/RexxNativeActivation.cpp
@@ -65,6 +65,7 @@
 #include "SystemInterpreter.hpp"
 #include "ActivationFrame.hpp"
 #include "StackFrameClass.hpp"
+#include "MutableBufferClass.hpp"
 
 #include <math.h>
 #include <limits.h>
@@ -564,6 +565,17 @@
                         case REXX_VALUE_POINTERSTRING:
                         {
                             descriptors[outputIndex].value.value_POINTERSTRING = this->pointerString(argument, inputIndex);
+                            break;
+                        }
+
+                        case REXX_VALUE_RexxMutableBufferObject:
+                        {
+                            // this must be a pointer object
+                            if (!argument->isInstanceOf(TheMutableBufferClass))
+                            {
+                                reportException(Error_Invalid_argument_noclass, inputIndex + 1, TheMutableBufferClass->getId());
+                            }
+                            descriptors[outputIndex].value.value_RexxMutableBufferObject = (RexxMutableBufferObject)argument;
                             break;
                         }
 
@@ -611,6 +623,7 @@
                         case REXX_VALUE_RexxArrayObject:   // no object here
                         case REXX_VALUE_RexxStemObject:
                         case REXX_VALUE_RexxClassObject:
+                        case REXX_VALUE_RexxMutableBufferObject:
                         case REXX_VALUE_POINTERSTRING:
                         {
                             // set this as a 64-bit value to clear everything out