diff --git a/src/librustc_llvm/ffi.rs b/src/librustc_llvm/ffi.rs
index dba2e918f6f3a..c1e32c7c0226e 100644
--- a/src/librustc_llvm/ffi.rs
+++ b/src/librustc_llvm/ffi.rs
@@ -1651,6 +1651,7 @@ extern "C" {
                                                MergeFunctions: bool,
                                                SLPVectorize: bool,
                                                LoopVectorize: bool,
+                                               PrepareForThinLTO: bool,
                                                PGOGenPath: *const c_char,
                                                PGOUsePath: *const c_char);
     pub fn LLVMRustAddLibraryInfo(PM: PassManagerRef,
diff --git a/src/librustc_trans/back/lto.rs b/src/librustc_trans/back/lto.rs
index 2a473f1ecbcc5..bbb5f7eecc82c 100644
--- a/src/librustc_trans/back/lto.rs
+++ b/src/librustc_trans/back/lto.rs
@@ -482,7 +482,7 @@ fn run_pass_manager(cgcx: &CodegenContext,
             llvm::CodeGenOptLevel::None => llvm::CodeGenOptLevel::Less,
             level => level,
         };
-        with_llvm_pmb(llmod, config, opt_level, &mut |b| {
+        with_llvm_pmb(llmod, config, opt_level, false, &mut |b| {
             if thin {
                 if !llvm::LLVMRustPassManagerBuilderPopulateThinLTOPassManager(b, pm) {
                     panic!("this version of LLVM does not support ThinLTO");
diff --git a/src/librustc_trans/back/write.rs b/src/librustc_trans/back/write.rs
index 64876e82309f0..57fe0729375f6 100644
--- a/src/librustc_trans/back/write.rs
+++ b/src/librustc_trans/back/write.rs
@@ -547,7 +547,8 @@ unsafe fn optimize(cgcx: &CodegenContext,
             llvm::LLVMRustAddAnalysisPasses(tm, fpm, llmod);
             llvm::LLVMRustAddAnalysisPasses(tm, mpm, llmod);
             let opt_level = config.opt_level.unwrap_or(llvm::CodeGenOptLevel::None);
-            with_llvm_pmb(llmod, &config, opt_level, &mut |b| {
+            let prepare_for_thin_lto = cgcx.lto == Lto::Thin || cgcx.lto == Lto::ThinLocal;
+            with_llvm_pmb(llmod, &config, opt_level, prepare_for_thin_lto, &mut |b| {
                 llvm::LLVMPassManagerBuilderPopulateFunctionPassManager(b, fpm);
                 llvm::LLVMPassManagerBuilderPopulateModulePassManager(b, mpm);
             })
@@ -2042,6 +2043,7 @@ pub fn run_assembler(cgcx: &CodegenContext, handler: &Handler, assembly: &Path,
 pub unsafe fn with_llvm_pmb(llmod: ModuleRef,
                             config: &ModuleConfig,
                             opt_level: llvm::CodeGenOptLevel,
+                            prepare_for_thin_lto: bool,
                             f: &mut FnMut(llvm::PassManagerBuilderRef)) {
     use std::ptr;
 
@@ -2069,6 +2071,7 @@ pub unsafe fn with_llvm_pmb(llmod: ModuleRef,
         config.merge_functions,
         config.vectorize_slp,
         config.vectorize_loop,
+        prepare_for_thin_lto,
         pgo_gen_path.as_ref().map_or(ptr::null(), |s| s.as_ptr()),
         pgo_use_path.as_ref().map_or(ptr::null(), |s| s.as_ptr()),
     );
diff --git a/src/rustllvm/PassWrapper.cpp b/src/rustllvm/PassWrapper.cpp
index 382ef2cc407dd..8593f543619a5 100644
--- a/src/rustllvm/PassWrapper.cpp
+++ b/src/rustllvm/PassWrapper.cpp
@@ -428,13 +428,16 @@ extern "C" void LLVMRustAddAnalysisPasses(LLVMTargetMachineRef TM,
 
 extern "C" void LLVMRustConfigurePassManagerBuilder(
     LLVMPassManagerBuilderRef PMBR, LLVMRustCodeGenOptLevel OptLevel,
-    bool MergeFunctions, bool SLPVectorize, bool LoopVectorize,
+    bool MergeFunctions, bool SLPVectorize, bool LoopVectorize, bool PrepareForThinLTO,
     const char* PGOGenPath, const char* PGOUsePath) {
   // Ignore mergefunc for now as enabling it causes crashes.
   // unwrap(PMBR)->MergeFunctions = MergeFunctions;
   unwrap(PMBR)->SLPVectorize = SLPVectorize;
   unwrap(PMBR)->OptLevel = fromRust(OptLevel);
   unwrap(PMBR)->LoopVectorize = LoopVectorize;
+#if LLVM_VERSION_GE(4, 0)
+  unwrap(PMBR)->PrepareForThinLTO = PrepareForThinLTO;
+#endif
 
 #ifdef PGO_AVAILABLE
   if (PGOGenPath) {