diff --git a/lib/Passes/PassBuilder.cpp b/lib/Passes/PassBuilder.cpp
index bb7d800f8b4..52f7026c40e 100644
--- a/lib/Passes/PassBuilder.cpp
+++ b/lib/Passes/PassBuilder.cpp
@@ -1539,8 +1539,17 @@ ModulePassManager PassBuilder::buildThinLTODefaultPipeline(
     MPM.addPass(LowerTypeTestsPass(nullptr, ImportSummary));
   }
 
-  if (Level == OptimizationLevel::O0)
+  if (Level == OptimizationLevel::O0) {
+    // Run a second time to clean up any type tests left behind by WPD for use
+    // in ICP.
+    MPM.addPass(LowerTypeTestsPass(nullptr, nullptr, true));
+    // Drop available_externally and unreferenced globals. This is necessary
+    // with ThinLTO in order to avoid leaving undefined references to dead
+    // globals in the object file.
+    MPM.addPass(EliminateAvailableExternallyPass());
+    MPM.addPass(GlobalDCEPass());
     return MPM;
+  }
 
   // Force any function attributes we want the rest of the pipeline to observe.
   MPM.addPass(ForceFunctionAttrsPass());
diff --git a/test/Other/new-pm-O0-defaults.ll b/test/Other/new-pm-O0-defaults.ll
index 8900a77b1f2..b7cd5ecae79 100644
--- a/test/Other/new-pm-O0-defaults.ll
+++ b/test/Other/new-pm-O0-defaults.ll
@@ -35,6 +35,9 @@
 ; CHECK-PRE-LINK-NEXT: Running pass: CanonicalizeAliasesPass
 ; CHECK-PRE-LINK-NEXT: Running pass: NameAnonGlobalPass
 ; CHECK-THINLTO-NEXT: Running pass: Annotation2MetadataPass
+; CHECK-THINLTO-NEXT: Running pass: LowerTypeTestsPass
+; CHECK-THINLTO-NEXT: Running pass: EliminateAvailableExternallyPass
+; CHECK-THINLTO-NEXT: Running pass: GlobalDCEPass
 ; CHECK-LTO-NEXT: Running pass: Annotation2MetadataPass
 ; CHECK-LTO-NEXT: Running pass: WholeProgramDevirtPass
 ; CHECK-LTO-NEXT: Running analysis: InnerAnalysisManagerProxy