diff --git a/src/ir/module/mod.rs b/src/ir/module/mod.rs
index fb01569..65c8032 100644
--- a/src/ir/module/mod.rs
+++ b/src/ir/module/mod.rs
@@ -243,13 +243,13 @@ impl<'a> Module<'a> {
                 }
                 Payload::CodeSectionEntry(body) => {
                     let locals_reader = body.get_locals_reader()?;
+                    let num_locals = locals_reader.get_count();
                     let locals = locals_reader.into_iter().collect::<Result<Vec<_>, _>>()?;
                     let locals: Vec<(u32, DataType)> = locals
                         .iter()
                         .map(|(idx, val_type)| (*idx, DataType::from(*val_type)))
                         .collect();
-                    // TODO: can I just iter locals once?
-                    let num_locals = locals.iter().fold(0, |acc, x| acc + x.0) as usize;
+
                     let instructions = body
                         .get_operators_reader()?
                         .into_iter()
diff --git a/src/ir/module/module_functions.rs b/src/ir/module/module_functions.rs
index 5801884..0f89532 100644
--- a/src/ir/module/module_functions.rs
+++ b/src/ir/module/module_functions.rs
@@ -186,10 +186,10 @@ impl<'a> LocalFunction<'a> {
 pub(crate) fn add_local(
     ty: DataType,
     num_params: usize,
-    num_locals: &mut usize,
+    num_locals: &mut u32,
     locals: &mut Vec<(u32, DataType)>,
 ) -> LocalID {
-    let index = num_params + *num_locals;
+    let index = num_params + *num_locals as usize;
 
     let len = locals.len();
     *num_locals += 1;
diff --git a/src/ir/types.rs b/src/ir/types.rs
index 6111dfd..f0419ba 100644
--- a/src/ir/types.rs
+++ b/src/ir/types.rs
@@ -832,7 +832,7 @@ pub struct Body<'a> {
     /// defined here then local indices 0 and 1 will refer to the parameters and
     /// index 2 will refer to the local here.
     pub locals: Vec<(u32, DataType)>,
-    pub num_locals: usize,
+    pub num_locals: u32,
     // accessing operators by .0 is not very clear
     pub instructions: Vec<Instruction<'a>>,
     pub num_instructions: usize,