diff --git a/wrap/Argument.h b/wrap/Argument.h
index 367d494c9..98a8ab7b1 100644
--- a/wrap/Argument.h
+++ b/wrap/Argument.h
@@ -173,7 +173,8 @@ struct ArgumentListGrammar: public classic::grammar<ArgumentListGrammar> {
 
   wrap::ArgumentList& result_; ///< successful parse will be placed in here
 
-  Argument arg, arg0;
+  const Argument arg0; // used to reset arg
+  mutable Argument arg; // temporary argument for use during parsing
   ArgumentGrammar argument_g;
 
   /// Construct type grammar and specify where result is placed
diff --git a/wrap/tests/testArgument.cpp b/wrap/tests/testArgument.cpp
index 31269c652..d99f9e4b3 100644
--- a/wrap/tests/testArgument.cpp
+++ b/wrap/tests/testArgument.cpp
@@ -95,16 +95,32 @@ TEST( ArgumentList, grammar ) {
   actual.clear();
 
   EXPECT(parse("(char a)", g, space_p).full);
+  EXPECT_LONGS_EQUAL(1, actual.size());
+  actual.clear();
 
   EXPECT(parse("(unsigned char a)", g, space_p).full);
+  EXPECT_LONGS_EQUAL(1, actual.size());
+  actual.clear();
 
   EXPECT(parse("(Vector v, Matrix m)", g, space_p).full);
+  EXPECT_LONGS_EQUAL(2, actual.size());
+  EXPECT(actual[0]==Argument(Qualified("Vector",Qualified::EIGEN),"v"));
+  EXPECT(actual[1]==Argument(Qualified("Matrix",Qualified::EIGEN),"m"));
+  actual.clear();
 
   EXPECT(parse("(Point2 p)", g, space_p).full);
+  EXPECT_LONGS_EQUAL(1, actual.size());
+  actual.clear();
 
   EXPECT(parse("(Point2 p1, Point3 p2)", g, space_p).full);
+  EXPECT_LONGS_EQUAL(2, actual.size());
+  EXPECT(actual[0]==Argument(Qualified("Point2"),"p1"));
+  EXPECT(actual[1]==Argument(Qualified("Point3"),"p2"));
+  actual.clear();
 
   EXPECT(parse("(gtsam::Point2 p3)", g, space_p).full);
+  EXPECT_LONGS_EQUAL(1, actual.size());
+  actual.clear();
 }
 
 /* ************************************************************************* */