diff --git a/compiler/gen_wasm/src/module_builder.rs b/compiler/gen_wasm/src/module_builder.rs
index cfa2de5f05..8051298300 100644
--- a/compiler/gen_wasm/src/module_builder.rs
+++ b/compiler/gen_wasm/src/module_builder.rs
@@ -270,7 +270,9 @@ impl<'a> FunctionSection<'a> {
 
 impl<'a> Serialize for FunctionSection<'a> {
     fn serialize<T: SerialBuffer>(&self, buffer: &mut T) {
-        todo!();
+        let header_indices = write_section_header(buffer, SectionId::Function);
+        serialize_vector_with_count(buffer, &self.signature_indices);
+        update_section_size(buffer, header_indices);
     }
 }
 
diff --git a/compiler/gen_wasm/src/serialize.rs b/compiler/gen_wasm/src/serialize.rs
index a261256a4a..2e8777b1b8 100644
--- a/compiler/gen_wasm/src/serialize.rs
+++ b/compiler/gen_wasm/src/serialize.rs
@@ -114,6 +114,12 @@ impl Serialize for str {
     }
 }
 
+impl Serialize for u32 {
+    fn serialize<T: SerialBuffer>(&self, buffer: &mut T) {
+        buffer.encode_u32(*self);
+    }
+}
+
 fn overwrite_padded_u32_help(buffer: &mut [u8], value: u32) {
     let mut x = value;
     for byte in buffer.iter_mut().take(4) {