diff --git a/clang-tools-extra/modularize/PreprocessorTracker.cpp b/clang-tools-extra/modularize/PreprocessorTracker.cpp
index 566e2f15a332..5776a6152af0 100644
--- a/clang-tools-extra/modularize/PreprocessorTracker.cpp
+++ b/clang-tools-extra/modularize/PreprocessorTracker.cpp
@@ -962,6 +962,8 @@ public:
                                  llvm::StringRef MacroUnexpanded,
                                  llvm::StringRef MacroExpanded,
                                  InclusionPathHandle InclusionPathHandle) {
+    if (InNestedHeader)
+      return;
     StringHandle MacroName = addString(II->getName());
     PPItemKey InstanceKey(PP, MacroName, H, InstanceLoc);
     PPItemKey DefinitionKey(PP, MacroName, H, DefinitionLoc);