diff --git a/crsn/src/builtin/parse.rs b/crsn/src/builtin/parse.rs
index e28f911..7ae516d 100644
--- a/crsn/src/builtin/parse.rs
+++ b/crsn/src/builtin/parse.rs
@@ -28,7 +28,7 @@ impl CrsnExtension for BuiltinOps {
         "builtin"
     }
 
-    fn parse_op(&self, keyword: &str, mut args: ArgParser) -> Result<ParseOpRes, Error> {
+    fn parse_op(&self, keyword: &str, mut args: ArgParser) -> Result<ParseOpRes<Op>, Error> {
         Ok(ParseOpRes::Parsed(Op::BuiltIn(match keyword {
             "nop" => {
                 BuiltinOp::Nop
diff --git a/crsn/src/module/mod.rs b/crsn/src/module/mod.rs
index a7abd66..5d023b8 100644
--- a/crsn/src/module/mod.rs
+++ b/crsn/src/module/mod.rs
@@ -14,13 +14,20 @@ use crate::runtime::run_thread::ThreadInfo;
 mod eval_res;
 
 /// Result type returned from the op parser. This is the Ok variant of a Result.
-pub enum ParseOpRes {
+pub enum ParseOpRes<T> {
     /// Parsing successful.
-    Parsed(Op),
+    Parsed(T),
     /// Instruction not recognized, but there was no error.
     Unknown(ArgParser),
 }
 
+impl ParseOpRes<Op> {
+    /// Helper to construct an extension op
+    pub fn parsed(op : impl OpTrait) -> Self {
+        Self::Parsed(Op::Ext(Box::new(op)))
+    }
+}
+
 pub trait OpTrait: Debug + Send + Sync + 'static {
     fn execute(&self, ti: &ThreadInfo, state: &mut RunState) -> Result<EvalRes, Fault>;
 }
@@ -34,7 +41,7 @@ pub trait CrsnExtension: Debug + Send + Sync + 'static {
     /// the argument list and either return Ok or Err.
     ///
     /// If the instruction keyword is not recognized, return Unknown with the unchanged argument list.
-    fn parse_op(&self, keyword: &str, arg_tokens: ArgParser) -> Result<ParseOpRes, Error>;
+    fn parse_op(&self, keyword: &str, arg_tokens: ArgParser) -> Result<ParseOpRes<Op>, Error>;
 
     /// Drop an object referenced by a handle
     fn drop_obj(&self,
diff --git a/crsn_arith/src/parse.rs b/crsn_arith/src/parse.rs
index d641302..316d216 100644
--- a/crsn_arith/src/parse.rs
+++ b/crsn_arith/src/parse.rs
@@ -24,8 +24,8 @@ impl CrsnExtension for ArithOps {
         "arith"
     }
 
-    fn parse_op(&self, keyword: &str, mut args: ArgParser) -> Result<ParseOpRes, Error> {
-        Ok(ParseOpRes::Parsed(Op::Ext(Box::new(match keyword {
+    fn parse_op(&self, keyword: &str, mut args: ArgParser) -> Result<ParseOpRes<Op>, Error> {
+        Ok(ParseOpRes::parsed(match keyword {
             "cmp" => {
                 ArithOp::Compare {
                     a: args.next_rd()?,
@@ -450,6 +450,6 @@ impl CrsnExtension for ArithOps {
             _other => {
                 return Ok(ParseOpRes::Unknown(args));
             }
-        }))))
+        }))
     }
 }
diff --git a/crsn_stacks/src/parse.rs b/crsn_stacks/src/parse.rs
index 3f028df..ee5bbbf 100644
--- a/crsn_stacks/src/parse.rs
+++ b/crsn_stacks/src/parse.rs
@@ -26,8 +26,8 @@ impl CrsnExtension for StackOps {
         "stacks"
     }
 
-    fn parse_op(&self, keyword: &str, mut args: ArgParser) -> Result<ParseOpRes, Error> {
-        Ok(ParseOpRes::Parsed(Op::Ext(Box::new(match keyword {
+    fn parse_op(&self, keyword: &str, mut args: ArgParser) -> Result<ParseOpRes<Op>, Error> {
+        Ok(ParseOpRes::parsed(match keyword {
             "stack" => {
                 StackOp::NewStack {
                     dst: args.next_wr()?,
@@ -51,7 +51,7 @@ impl CrsnExtension for StackOps {
             _other => {
                 return Ok(ParseOpRes::Unknown(args));
             }
-        }))))
+        }))
     }
 
     fn drop_obj(&self, _ti: &ThreadInfo, state: &mut RunState, handle: Value) -> Result<Option<()>, Fault>