diff --git a/clang-tools-extra/clangd/IncludeFixer.cpp b/clang-tools-extra/clangd/IncludeFixer.cpp
--- a/clang-tools-extra/clangd/IncludeFixer.cpp
+++ b/clang-tools-extra/clangd/IncludeFixer.cpp
@@ -40,6 +40,7 @@
 #include "llvm/ADT/StringSet.h"
 #include "llvm/Support/Error.h"
 #include "llvm/Support/FormatVariadic.h"
+#include <set>
 #include <vector>
 
 namespace clang {
@@ -313,18 +314,18 @@
 std::vector<std::string>
 collectAccessibleScopes(Sema &Sem, const DeclarationNameInfo &Typo, Scope *S,
                         Sema::LookupNameKind LookupKind) {
-  std::vector<std::string> Scopes;
   VisitedContextCollector Collector;
   Sem.LookupVisibleDecls(S, LookupKind, Collector,
                          /*IncludeGlobalScope=*/false,
                          /*LoadExternal=*/false);
 
-  Scopes.push_back("");
+  std::set<std::string> Scopes;
+  Scopes.insert("");
   for (const auto *Ctx : Collector.takeVisitedContexts()) {
     if (isa<NamespaceDecl>(Ctx))
-      Scopes.push_back(printNamespaceScope(*Ctx));
+      Scopes.insert(printNamespaceScope(*Ctx));
   }
-  return Scopes;
+  return {Scopes.begin(), Scopes.end()};
 }
 
 class IncludeFixer::UnresolvedNameRecorder : public ExternalSemaSource {