diff --git a/csbindgen-tests/build.rs b/csbindgen-tests/build.rs
index 83c4b05..d03a73b 100644
--- a/csbindgen-tests/build.rs
+++ b/csbindgen-tests/build.rs
@@ -91,6 +91,14 @@ fn main() -> Result<(), Box<dyn Error>> {
         .generate_csharp_file("../dotnet-sandbox/NativeMethods.cs")
         .unwrap();
 
+    csbindgen::Builder::default()
+        .input_extern_file("src/nested_module_test.rs")
+        .csharp_class_name("NestedModuleTests")
+        .csharp_dll_name("csbindgen_tests_nested_module")
+        .csharp_use_function_pointer(true)
+        .generate_csharp_file("../dotnet-sandbox/NestedModuleTests.cs")
+        .unwrap();
+    
     csbindgen::Builder::new()
         .input_bindgen_file("src/zstd.rs")
         .method_filter(|x| x.starts_with("ZSTD_"))
diff --git a/csbindgen-tests/src/nested_module_test.rs b/csbindgen-tests/src/nested_module_test.rs
new file mode 100644
index 0000000..38588fc
--- /dev/null
+++ b/csbindgen-tests/src/nested_module_test.rs
@@ -0,0 +1,31 @@
+mod nested_mod {
+    #[repr(C)]
+    pub struct NumberStruct {
+        pub num: i32,
+    }
+    type NumberStructAlias = NumberStruct;
+    #[no_mangle]
+    pub extern "C" fn triple_input(input: NumberStruct) -> i32 {
+        input.num * 3
+    }
+    #[no_mangle]
+    pub extern "C" fn triple_input_aliased(input: NumberStructAlias) -> i32 {
+        input.num * 3
+    }
+    
+    #[repr(u8)]
+    pub enum NumberEnum {
+        One,
+        Two,
+        Three,
+    }
+    #[no_mangle]
+    pub extern "C" fn number_map(input: NumberEnum) -> i32 {
+        match input { 
+            NumberEnum::One => 1,
+            NumberEnum::Two => 2,
+            NumberEnum::Three => 3,
+            _ => -1
+        }
+    }
+}
\ No newline at end of file
diff --git a/csbindgen/src/parser.rs b/csbindgen/src/parser.rs
index f7ddeb1..0f2ff2b 100644
--- a/csbindgen/src/parser.rs
+++ b/csbindgen/src/parser.rs
@@ -8,12 +8,33 @@ enum FnItem {
     Item(syn::ItemFn),
 }
 
+/// build a Vec of all Items, unless the Item is a Item::Mod, then append the Item contents of the vect
+/// Do this recursively
+fn depth_first_module_walk<'a>(ast: &'a Vec<Item>) -> Vec<&'a syn::Item>{
+    let mut unwrapped_items : Vec<&syn::Item> = vec![];
+    for item in ast {
+        match item {
+            Item::Mod(m) => match &m.content {
+                Some((_, items)) => {
+                    unwrapped_items.extend(depth_first_module_walk(items));
+                }
+                _ => {}
+            },
+            _ => {
+                unwrapped_items.push(item);
+            }
+        }
+    }
+    
+    unwrapped_items
+}
+
 pub fn collect_foreign_method(
     ast: &syn::File,
     options: &BindgenOptions,
     list: &mut Vec<ExternMethod>,
 ) {
-    for item in ast.items.iter() {
+    for item in depth_first_module_walk(&ast.items) {
         if let Item::ForeignMod(m) = item {
             for item in m.items.iter() {
                 if let ForeignItem::Fn(m) = item {
@@ -32,7 +53,7 @@ pub fn collect_extern_method(
     options: &BindgenOptions,
     list: &mut Vec<ExternMethod>,
 ) {
-    for item in ast.items.iter() {
+    for item in depth_first_module_walk(&ast.items) {
         if let Item::Fn(m) = item {
             if m.sig.abi.is_some() {
                 // has extern
@@ -112,7 +133,7 @@ fn parse_method(item: FnItem, options: &BindgenOptions) -> Option<ExternMethod>
 }
 
 pub fn collect_type_alias(ast: &syn::File, result: &mut AliasMap) {
-    for item in ast.items.iter() {
+    for item in depth_first_module_walk(&ast.items) {
         if let Item::Type(t) = item {
             let name = t.ident.to_string();
             let alias = parse_type(&t.ty);
@@ -137,7 +158,7 @@ pub fn collect_type_alias(ast: &syn::File, result: &mut AliasMap) {
 
 pub fn collect_struct(ast: &syn::File, result: &mut Vec<RustStruct>) {
     // collect union or struct
-    for item in ast.items.iter() {
+    for item in depth_first_module_walk(&ast.items) {
         if let Item::Union(t) = item {
             let struct_name = t.ident.to_string();
             let fields = collect_fields(&t.fields);
@@ -211,7 +232,7 @@ fn collect_fields_unnamed(fields: &syn::FieldsUnnamed) -> Vec<FieldMember> {
 }
 
 pub fn collect_enum(ast: &syn::File, result: &mut Vec<RustEnum>) {
-    for item in ast.items.iter() {
+    for item in depth_first_module_walk(&ast.items) {
         if let Item::Enum(t) = item {
             let mut repr = None;
             for attr in &t.attrs {
diff --git a/dotnet-sandbox/NestedModuleTests.cs b/dotnet-sandbox/NestedModuleTests.cs
new file mode 100644
index 0000000..3013429
--- /dev/null
+++ b/dotnet-sandbox/NestedModuleTests.cs
@@ -0,0 +1,44 @@
+// <auto-generated>
+// This code is generated by csbindgen.
+// DON'T CHANGE THIS DIRECTLY.
+// </auto-generated>
+#pragma warning disable CS8500
+#pragma warning disable CS8981
+using System;
+using System.Runtime.InteropServices;
+
+namespace CsBindgen
+{
+    internal static unsafe partial class NestedModuleTests
+    {
+        const string __DllName = "csbindgen_tests_nested_module";
+
+        [DllImport(__DllName, EntryPoint = "triple_input", CallingConvention = CallingConvention.Cdecl, ExactSpelling = true)]
+        public static extern int triple_input(NumberStruct input);
+
+        [DllImport(__DllName, EntryPoint = "triple_input_aliased", CallingConvention = CallingConvention.Cdecl, ExactSpelling = true)]
+        public static extern int triple_input_aliased(NumberStruct input);
+
+        [DllImport(__DllName, EntryPoint = "number_map", CallingConvention = CallingConvention.Cdecl, ExactSpelling = true)]
+        public static extern int number_map(NumberEnum input);
+
+
+    }
+
+    [StructLayout(LayoutKind.Sequential)]
+    internal unsafe partial struct NumberStruct
+    {
+        public int num;
+    }
+
+
+    internal enum NumberEnum : byte
+    {
+        One,
+        Two,
+        Three,
+    }
+
+
+}
+    
\ No newline at end of file