diff --git a/src/bin/dmc/name_analysis.rs b/src/bin/dmc/name_analysis.rs
index b4c4e31..26ff680 100644
--- a/src/bin/dmc/name_analysis.rs
+++ b/src/bin/dmc/name_analysis.rs
@@ -31,7 +31,7 @@ pub fn name_analysis(paths: &Vec<PathBuf>) -> Result<(), Box<dyn std::error::Err
     let mut symbol_table = SymbolTable::new();
     add_std_core_symbols(&mut symbol_table).expect("Failed to add std::core symbols.");
 
-    let diagnostics = analyze_names(compilation_units.as_mut_slice(), &files, &mut symbol_table);
+    let diagnostics = analyze_names(&compilation_units, &files, &mut symbol_table);
     if diagnostics.is_empty() {
         println!("Name analysis complete.");
         println!("{}", symbol_table);
diff --git a/src/name_analysis/gather.rs b/src/name_analysis/gather.rs
index f3df01d..be51957 100644
--- a/src/name_analysis/gather.rs
+++ b/src/name_analysis/gather.rs
@@ -334,7 +334,7 @@ fn gather_node<'a>(
 }
 
 pub fn gather_compilation_unit<'a>(
-    compilation_unit: &'a mut CompilationUnit,
+    compilation_unit: &'a CompilationUnit,
     file_name: &str,
     symbol_table: &mut SymbolTable,
     scope_ids: &mut HashMap<&'a VariableUse, usize>,
diff --git a/src/name_analysis/mod.rs b/src/name_analysis/mod.rs
index 6f38c6b..878a2f0 100644
--- a/src/name_analysis/mod.rs
+++ b/src/name_analysis/mod.rs
@@ -34,7 +34,7 @@ pub mod symbol;
 pub mod symbol_table;
 
 pub fn analyze_names<'a, F: Files<'a, FileId = usize, Name = String>>(
-    compilation_units: &mut [Box<CompilationUnit>],
+    compilation_units: &[Box<CompilationUnit>],
     files: &'a F,
     symbol_table: &mut SymbolTable,
 ) -> Vec<DmDiagnostic> {
@@ -42,7 +42,7 @@ pub fn analyze_names<'a, F: Files<'a, FileId = usize, Name = String>>(
     let mut scope_ids: HashMap<&VariableUse, usize> = HashMap::new();
 
     // gather symbols
-    for compilation_unit in compilation_units.iter_mut() {
+    for compilation_unit in compilation_units {
         let file_name = files.name(compilation_unit.file_id()).unwrap();
         gather_compilation_unit(
             compilation_unit,
@@ -54,7 +54,7 @@ pub fn analyze_names<'a, F: Files<'a, FileId = usize, Name = String>>(
     }
 
     // resolve symbols
-    for compilation_unit in compilation_units.iter_mut() {
+    for compilation_unit in compilation_units {
         // resolve_compilation_unit(compilation_unit, symbol_table, &mut diagnostics);
     }