diff --git a/compiler/rustc_codegen_gcc/src/lib.rs b/compiler/rustc_codegen_gcc/src/lib.rs
index 3c4daeb51e47..7fd9c28c43f2 100644
--- a/compiler/rustc_codegen_gcc/src/lib.rs
+++ b/compiler/rustc_codegen_gcc/src/lib.rs
@@ -86,9 +86,7 @@
 };
 use rustc_codegen_ssa::base::codegen_crate;
 use rustc_codegen_ssa::target_features::cfg_target_feature;
-use rustc_codegen_ssa::traits::{
-    CodegenBackend, ExtraBackendMethods, ModuleBufferMethods, WriteBackendMethods,
-};
+use rustc_codegen_ssa::traits::{CodegenBackend, ExtraBackendMethods, WriteBackendMethods};
 use rustc_codegen_ssa::{CodegenResults, CompiledModule, ModuleCodegen, TargetConfig};
 use rustc_data_structures::fx::FxIndexMap;
 use rustc_data_structures::profiling::SelfProfilerRef;
@@ -423,20 +421,11 @@ unsafe impl Send for SyncContext {}
 // FIXME(antoyo): that shouldn't be Sync. Parallel compilation is currently disabled with "CodegenBackend::supports_parallel()".
 unsafe impl Sync for SyncContext {}
 
-pub struct ThinBuffer;
-
-impl ModuleBufferMethods for ThinBuffer {
-    fn data(&self) -> &[u8] {
-        &[]
-    }
-}
-
 impl WriteBackendMethods for GccCodegenBackend {
     type Module = GccContext;
     type TargetMachine = ();
     type ModuleBuffer = ModuleBuffer;
     type ThinData = ();
-    type ThinBuffer = ThinBuffer;
 
     fn run_and_optimize_fat_lto(
         cgcx: &CodegenContext,
@@ -458,7 +447,7 @@ fn run_thin_lto(
         // FIXME(bjorn3): Limit LTO exports to these symbols
         _exported_symbols_for_lto: &[String],
         _each_linked_rlib_for_lto: &[PathBuf],
-        _modules: Vec<(String, Self::ThinBuffer)>,
+        _modules: Vec<(String, Self::ModuleBuffer)>,
         _cached_modules: Vec<(SerializedModule<Self::ModuleBuffer>, WorkProduct)>,
     ) -> (Vec<ThinModule<Self>>, Vec<WorkProduct>) {
         unreachable!()
@@ -502,11 +491,7 @@ fn codegen(
         back::write::codegen(cgcx, prof, shared_emitter, module, config)
     }
 
-    fn prepare_thin(_module: Self::Module) -> Self::ThinBuffer {
-        unreachable!()
-    }
-
-    fn serialize_module(_module: Self::Module) -> Self::ModuleBuffer {
+    fn serialize_module(_module: Self::Module, _is_thin: bool) -> Self::ModuleBuffer {
         unimplemented!();
     }
 }
diff --git a/compiler/rustc_codegen_llvm/src/lib.rs b/compiler/rustc_codegen_llvm/src/lib.rs
index 5325783c3b21..7120ee0afec9 100644
--- a/compiler/rustc_codegen_llvm/src/lib.rs
+++ b/compiler/rustc_codegen_llvm/src/lib.rs
@@ -153,7 +153,6 @@ impl WriteBackendMethods for LlvmCodegenBackend {
     type ModuleBuffer = back::lto::ModuleBuffer;
     type TargetMachine = OwnedTargetMachine;
     type ThinData = back::lto::ThinData;
-    type ThinBuffer = back::lto::ModuleBuffer;
     fn print_pass_timings(&self) {
         let timings = llvm::build_string(|s| unsafe { llvm::LLVMRustPrintPassTimings(s) }).unwrap();
         print!("{timings}");
@@ -193,7 +192,7 @@ fn run_thin_lto(
         dcx: DiagCtxtHandle<'_>,
         exported_symbols_for_lto: &[String],
         each_linked_rlib_for_lto: &[PathBuf],
-        modules: Vec<(String, Self::ThinBuffer)>,
+        modules: Vec<(String, Self::ModuleBuffer)>,
         cached_modules: Vec<(SerializedModule<Self::ModuleBuffer>, WorkProduct)>,
     ) -> (Vec<ThinModule<Self>>, Vec<WorkProduct>) {
         back::lto::run_thin(
@@ -233,11 +232,8 @@ fn codegen(
     ) -> CompiledModule {
         back::write::codegen(cgcx, prof, shared_emitter, module, config)
     }
-    fn prepare_thin(module: Self::Module) -> Self::ThinBuffer {
-        back::lto::ModuleBuffer::new(module.llmod(), true)
-    }
-    fn serialize_module(module: Self::Module) -> Self::ModuleBuffer {
-        back::lto::ModuleBuffer::new(module.llmod(), false)
+    fn serialize_module(module: Self::Module, is_thin: bool) -> Self::ModuleBuffer {
+        back::lto::ModuleBuffer::new(module.llmod(), is_thin)
     }
 }
 
diff --git a/compiler/rustc_codegen_ssa/src/back/lto.rs b/compiler/rustc_codegen_ssa/src/back/lto.rs
index 80b3b5a4d7c0..a2c951c16d28 100644
--- a/compiler/rustc_codegen_ssa/src/back/lto.rs
+++ b/compiler/rustc_codegen_ssa/src/back/lto.rs
@@ -42,7 +42,7 @@ pub fn data(&self) -> &[u8] {
 
 pub struct ThinShared<B: WriteBackendMethods> {
     pub data: B::ThinData,
-    pub thin_buffers: Vec<B::ThinBuffer>,
+    pub thin_buffers: Vec<B::ModuleBuffer>,
     pub serialized_modules: Vec<SerializedModule<B::ModuleBuffer>>,
     pub module_names: Vec<CString>,
 }
diff --git a/compiler/rustc_codegen_ssa/src/back/write.rs b/compiler/rustc_codegen_ssa/src/back/write.rs
index 81c45f12de7b..9898c1296142 100644
--- a/compiler/rustc_codegen_ssa/src/back/write.rs
+++ b/compiler/rustc_codegen_ssa/src/back/write.rs
@@ -362,7 +362,7 @@ fn generate_thin_lto_work<B: ExtraBackendMethods>(
     dcx: DiagCtxtHandle<'_>,
     exported_symbols_for_lto: &[String],
     each_linked_rlib_for_lto: &[PathBuf],
-    needs_thin_lto: Vec<(String, B::ThinBuffer)>,
+    needs_thin_lto: Vec<(String, B::ModuleBuffer)>,
     import_only_modules: Vec<(SerializedModule<B::ModuleBuffer>, WorkProduct)>,
 ) -> Vec<(ThinLtoWorkItem<B>, u64)> {
     let _prof_timer = prof.generic_activity("codegen_thin_generate_lto_work");
@@ -416,7 +416,7 @@ enum MaybeLtoModules<B: WriteBackendMethods> {
         cgcx: CodegenContext,
         exported_symbols_for_lto: Arc<Vec<String>>,
         each_linked_rlib_file_for_lto: Vec<PathBuf>,
-        needs_thin_lto: Vec<(String, <B as WriteBackendMethods>::ThinBuffer)>,
+        needs_thin_lto: Vec<(String, <B as WriteBackendMethods>::ModuleBuffer)>,
         lto_import_only_modules:
             Vec<(SerializedModule<<B as WriteBackendMethods>::ModuleBuffer>, WorkProduct)>,
     },
@@ -793,7 +793,7 @@ pub(crate) enum WorkItemResult<B: WriteBackendMethods> {
 
     /// The backend has finished compiling a CGU, which now needs to go through
     /// thin LTO.
-    NeedsThinLto(String, B::ThinBuffer),
+    NeedsThinLto(String, B::ModuleBuffer),
 }
 
 pub enum FatLtoInput<B: WriteBackendMethods> {
@@ -868,7 +868,7 @@ fn execute_optimize_work_item<B: ExtraBackendMethods>(
             WorkItemResult::Finished(module)
         }
         ComputedLtoType::Thin => {
-            let thin_buffer = B::prepare_thin(module.module_llvm);
+            let thin_buffer = B::serialize_module(module.module_llvm, true);
             if let Some(path) = bitcode {
                 fs::write(&path, thin_buffer.data()).unwrap_or_else(|e| {
                     panic!("Error writing pre-lto-bitcode file `{}`: {}", path.display(), e);
@@ -878,7 +878,7 @@ fn execute_optimize_work_item<B: ExtraBackendMethods>(
         }
         ComputedLtoType::Fat => match bitcode {
             Some(path) => {
-                let buffer = B::serialize_module(module.module_llvm);
+                let buffer = B::serialize_module(module.module_llvm, false);
                 fs::write(&path, buffer.data()).unwrap_or_else(|e| {
                     panic!("Error writing pre-lto-bitcode file `{}`: {}", path.display(), e);
                 });
@@ -1020,7 +1020,7 @@ fn do_thin_lto<B: ExtraBackendMethods>(
     tm_factory: TargetMachineFactoryFn<B>,
     exported_symbols_for_lto: Arc<Vec<String>>,
     each_linked_rlib_for_lto: Vec<PathBuf>,
-    needs_thin_lto: Vec<(String, <B as WriteBackendMethods>::ThinBuffer)>,
+    needs_thin_lto: Vec<(String, <B as WriteBackendMethods>::ModuleBuffer)>,
     lto_import_only_modules: Vec<(
         SerializedModule<<B as WriteBackendMethods>::ModuleBuffer>,
         WorkProduct,
@@ -1804,7 +1804,7 @@ enum CodegenState {
                 ));
             } else {
                 if let Some(allocator_module) = allocator_module.take() {
-                    let thin_buffer = B::prepare_thin(allocator_module.module_llvm);
+                    let thin_buffer = B::serialize_module(allocator_module.module_llvm, true);
                     needs_thin_lto.push((allocator_module.name, thin_buffer));
                 }
 
diff --git a/compiler/rustc_codegen_ssa/src/traits/write.rs b/compiler/rustc_codegen_ssa/src/traits/write.rs
index b0c065642f39..d33dfc1d014b 100644
--- a/compiler/rustc_codegen_ssa/src/traits/write.rs
+++ b/compiler/rustc_codegen_ssa/src/traits/write.rs
@@ -15,7 +15,6 @@ pub trait WriteBackendMethods: Clone + 'static {
     type TargetMachine;
     type ModuleBuffer: ModuleBufferMethods;
     type ThinData: Send + Sync;
-    type ThinBuffer: ModuleBufferMethods;
 
     /// Performs fat LTO by merging all modules into a single one, running autodiff
     /// if necessary and running any further optimizations
@@ -37,7 +36,7 @@ fn run_thin_lto(
         dcx: DiagCtxtHandle<'_>,
         exported_symbols_for_lto: &[String],
         each_linked_rlib_for_lto: &[PathBuf],
-        modules: Vec<(String, Self::ThinBuffer)>,
+        modules: Vec<(String, Self::ModuleBuffer)>,
         cached_modules: Vec<(SerializedModule<Self::ModuleBuffer>, WorkProduct)>,
     ) -> (Vec<ThinModule<Self>>, Vec<WorkProduct>);
     fn print_pass_timings(&self);
@@ -63,8 +62,7 @@ fn codegen(
         module: ModuleCodegen<Self::Module>,
         config: &ModuleConfig,
     ) -> CompiledModule;
-    fn prepare_thin(module: Self::Module) -> Self::ThinBuffer;
-    fn serialize_module(module: Self::Module) -> Self::ModuleBuffer;
+    fn serialize_module(module: Self::Module, is_thin: bool) -> Self::ModuleBuffer;
 }
 
 pub trait ModuleBufferMethods: Send + Sync {