Index: clangd/index/Background.cpp
===================================================================
--- clangd/index/Background.cpp
+++ clangd/index/Background.cpp
@@ -306,17 +306,20 @@
 
   // Build and store new slabs for each updated file.
   for (const auto &I : *Index.Sources) {
+    // We already have the map from uris to absolutepaths in the cache,
+    // therefore traverse Index.Sources rather than Files to get rid of absolute
+    // path to uri conversion.
     std::string Path = URICache.resolve(I.first());
+    auto FileIt = Files.find(Path);
+    if (FileIt == Files.end())
+      continue;
     SymbolSlab::Builder Syms;
     RefSlab::Builder Refs;
-    auto FileIt = Files.find(Path);
-    if (FileIt != Files.end()) {
-      auto &F = *FileIt;
-      for (const auto *S : F.second.Symbols)
-        Syms.insert(*S);
-      for (const auto *R : F.second.Refs)
-        Refs.insert(RefToIDs[R], *R);
-    }
+    auto &F = *FileIt;
+    for (const auto *S : F.second.Symbols)
+      Syms.insert(*S);
+    for (const auto *R : F.second.Refs)
+      Refs.insert(RefToIDs[R], *R);
     auto SS = llvm::make_unique<SymbolSlab>(std::move(Syms).build());
     auto RS = llvm::make_unique<RefSlab>(std::move(Refs).build());
     auto IG = llvm::make_unique<IncludeGraph>(
Index: unittests/clangd/BackgroundIndexTests.cpp
===================================================================
--- unittests/clangd/BackgroundIndexTests.cpp
+++ unittests/clangd/BackgroundIndexTests.cpp
@@ -351,8 +351,11 @@
   EXPECT_EQ(CacheHits, 2U); // Check both A.cc and A.h loaded from cache.
 
   // Check if the new symbol has arrived.
-  auto ShardSource = MSS.loadShard(testPath("root/A.cc"));
+  ShardHeader = MSS.loadShard(testPath("root/A.h"));
   EXPECT_NE(ShardHeader, nullptr);
+  EXPECT_THAT(*ShardHeader->Symbols, Contains(Named("A_CCnew")));
+  auto ShardSource = MSS.loadShard(testPath("root/A.cc"));
+  EXPECT_NE(ShardSource, nullptr);
   EXPECT_THAT(*ShardSource->Symbols,
               Contains(AllOf(Named("f_b"), Declared(), Defined())));
 }