diff --git a/llvm/include/llvm/Transforms/IPO/FunctionImport.h b/llvm/include/llvm/Transforms/IPO/FunctionImport.h
--- a/llvm/include/llvm/Transforms/IPO/FunctionImport.h
+++ b/llvm/include/llvm/Transforms/IPO/FunctionImport.h
@@ -111,7 +111,8 @@
         ClearDSOLocalOnDeclarations(ClearDSOLocalOnDeclarations) {}
 
   /// Import functions in Module \p M based on the supplied import list.
-  Expected<bool> importFunctions(Module &M, const ImportMapTy &ImportList);
+  Expected<bool> importFunctions(Module &M, const ImportMapTy &ImportList,
+                                 bool AssumeValidDebugInfo);
 
 private:
   /// The summaries index used to trigger importing.
diff --git a/llvm/lib/LTO/LTOBackend.cpp b/llvm/lib/LTO/LTOBackend.cpp
--- a/llvm/lib/LTO/LTOBackend.cpp
+++ b/llvm/lib/LTO/LTOBackend.cpp
@@ -648,7 +648,10 @@
 
   FunctionImporter Importer(CombinedIndex, ModuleLoader,
                             ClearDSOLocalOnDeclarations);
-  if (Error Err = Importer.importFunctions(Mod, ImportList).takeError())
+  if (Error Err =
+          Importer
+              .importFunctions(Mod, ImportList, /*AssumeValidDebugInfo=*/true)
+              .takeError())
     return Err;
 
   if (Conf.PostImportModuleHook && !Conf.PostImportModuleHook(Task, Mod))
diff --git a/llvm/lib/LTO/ThinLTOCodeGenerator.cpp b/llvm/lib/LTO/ThinLTOCodeGenerator.cpp
--- a/llvm/lib/LTO/ThinLTOCodeGenerator.cpp
+++ b/llvm/lib/LTO/ThinLTOCodeGenerator.cpp
@@ -221,7 +221,8 @@
   };
 
   FunctionImporter Importer(Index, Loader, ClearDSOLocalOnDeclarations);
-  Expected<bool> Result = Importer.importFunctions(TheModule, ImportList);
+  Expected<bool> Result = Importer.importFunctions(
+      TheModule, ImportList, /*AssumeValidDebugInfo=*/true);
   if (!Result) {
     handleAllErrors(Result.takeError(), [&](ErrorInfoBase &EIB) {
       SMDiagnostic Err = SMDiagnostic(TheModule.getModuleIdentifier(),
diff --git a/llvm/lib/Transforms/IPO/FunctionImport.cpp b/llvm/lib/Transforms/IPO/FunctionImport.cpp
--- a/llvm/lib/Transforms/IPO/FunctionImport.cpp
+++ b/llvm/lib/Transforms/IPO/FunctionImport.cpp
@@ -1252,7 +1252,8 @@
 // Automatically import functions in Module \p DestModule based on the summaries
 // index.
 Expected<bool> FunctionImporter::importFunctions(
-    Module &DestModule, const FunctionImporter::ImportMapTy &ImportList) {
+    Module &DestModule, const FunctionImporter::ImportMapTy &ImportList,
+    bool AssumeValidDebugInfo) {
   LLVM_DEBUG(dbgs() << "Starting import for Module "
                     << DestModule.getModuleIdentifier() << "\n");
   unsigned ImportedCount = 0, ImportedGVCount = 0;
@@ -1351,7 +1352,8 @@
 
     // Upgrade debug info after we're done materializing all the globals and we
     // have loaded all the required metadata!
-    UpgradeDebugInfo(*SrcModule);
+    if (!AssumeValidDebugInfo)
+      UpgradeDebugInfo(*SrcModule);
 
     // Set the partial sample profile ratio in the profile summary module flag
     // of the imported source module, if applicable, so that the profile summary
@@ -1443,7 +1445,8 @@
   };
   FunctionImporter Importer(*Index, ModuleLoader,
                             /*ClearDSOLocalOnDeclarations=*/false);
-  Expected<bool> Result = Importer.importFunctions(M, ImportList);
+  Expected<bool> Result =
+      Importer.importFunctions(M, ImportList, /*AssumeValidDebugInfo=*/false);
 
   // FIXME: Probably need to propagate Errors through the pass manager.
   if (!Result) {
diff --git a/llvm/test/LTO/X86/strip-debug-info.ll b/llvm/test/LTO/X86/strip-debug-info.ll
--- a/llvm/test/LTO/X86/strip-debug-info.ll
+++ b/llvm/test/LTO/X86/strip-debug-info.ll
@@ -5,25 +5,6 @@
 ; RUN:     -o %t.o %t.bc 2>&1 | \
 ; RUN:     FileCheck %s -allow-empty -check-prefix=CHECK-WARN
 ; RUN: llvm-nm %t.o | FileCheck %s 
-; ---- Thin LTO (codegen only) ------------------------------
-; RUN: llvm-lto -thinlto -thinlto-action=codegen \
-; RUN:     %t.bc -disable-verify 2>&1 | \
-; RUN:     FileCheck %s -allow-empty -check-prefix=CHECK-WARN
-; ---- Thin LTO (optimize, strip main file) -----------------
-; RUN: opt -disable-verify -disable-upgrade-debug-info -module-summary %s -o %t.bc
-; RUN: opt -disable-verify -disable-upgrade-debug-info -module-summary %S/Inputs/strip-debug-info-bar.ll \
-; RUN:     -o %t2.bc
-; RUN: llvm-lto -thinlto -thinlto-action=run \
-; RUN:     %t.bc -disable-verify 2>&1 | \
-; RUN:     FileCheck %s -allow-empty -check-prefix=CHECK-WARN
-; ---- Thin LTO (optimize, strip imported file) -------------
-; RUN: opt -module-summary %t.bc -o %t-stripped.bc
-; RUN: llvm-lto -thinlto-action=thinlink -o %t.index.bc %t-stripped.bc %t2.bc
-; RUN: llvm-lto -thinlto -thinlto-action=import \
-; RUN:     -thinlto-index=%t.index.bc \
-; RUN:     -exported-symbol foo -exported-symbol _foo \
-; RUN:     %t-stripped.bc -disable-verify 2>&1 | \
-; RUN:     FileCheck %s -allow-empty -check-prefix=CHECK-WARN
 
 ; CHECK-WARN: warning{{.*}} ignoring invalid debug info
 ; CHECK-WARN-NOT: Broken module found
diff --git a/llvm/tools/llvm-link/llvm-link.cpp b/llvm/tools/llvm-link/llvm-link.cpp
--- a/llvm/tools/llvm-link/llvm-link.cpp
+++ b/llvm/tools/llvm-link/llvm-link.cpp
@@ -368,7 +368,8 @@
   };
   FunctionImporter Importer(*Index, CachedModuleLoader,
                             /*ClearDSOLocalOnDeclarations=*/false);
-  ExitOnErr(Importer.importFunctions(DestModule, ImportList));
+  ExitOnErr(Importer.importFunctions(DestModule, ImportList,
+                                     /*AssumeValidDebugInfo=*/false));
 
   return true;
 }