diff --git a/clang-tools-extra/clangd/GlobalCompilationDatabase.h b/clang-tools-extra/clangd/GlobalCompilationDatabase.h
--- a/clang-tools-extra/clangd/GlobalCompilationDatabase.h
+++ b/clang-tools-extra/clangd/GlobalCompilationDatabase.h
@@ -119,7 +119,6 @@
 getQueryDriverDatabase(llvm::ArrayRef<std::string> QueryDriverGlobs,
                        std::unique_ptr<GlobalCompilationDatabase> Base);
 
-
 /// Wraps another compilation database, and supports overriding the commands
 /// using an in-memory mapping.
 class OverlayCDB : public GlobalCompilationDatabase {
@@ -134,6 +133,10 @@
   llvm::Optional<tooling::CompileCommand>
   getCompileCommand(PathRef File) const override;
   tooling::CompileCommand getFallbackCommand(PathRef File) const override;
+  /// Note that project info is gathered purely from the inner compilation
+  /// database. This is to ensure consistency, as a translation unit with an
+  /// overriden command might yield a different project compared to headers
+  /// included in it (or before and after the override arrives).
   llvm::Optional<ProjectInfo> getProjectInfo(PathRef File) const override;
 
   /// Sets or clears the compilation command for a particular file.
diff --git a/clang-tools-extra/clangd/GlobalCompilationDatabase.cpp b/clang-tools-extra/clangd/GlobalCompilationDatabase.cpp
--- a/clang-tools-extra/clangd/GlobalCompilationDatabase.cpp
+++ b/clang-tools-extra/clangd/GlobalCompilationDatabase.cpp
@@ -298,15 +298,8 @@
 }
 
 llvm::Optional<ProjectInfo> OverlayCDB::getProjectInfo(PathRef File) const {
-  {
-    std::lock_guard<std::mutex> Lock(Mutex);
-    auto It = Commands.find(removeDots(File));
-    if (It != Commands.end())
-      return ProjectInfo{};
-  }
   if (Base)
     return Base->getProjectInfo(File);
-
   return llvm::None;
 }
 } // namespace clangd
diff --git a/clang-tools-extra/clangd/unittests/GlobalCompilationDatabaseTests.cpp b/clang-tools-extra/clangd/unittests/GlobalCompilationDatabaseTests.cpp
--- a/clang-tools-extra/clangd/unittests/GlobalCompilationDatabaseTests.cpp
+++ b/clang-tools-extra/clangd/unittests/GlobalCompilationDatabaseTests.cpp
@@ -313,9 +313,22 @@
   llvm::sys::path::append(File, "blabla", "..", "a.cc");
 
   EXPECT_TRUE(DB.getCompileCommand(File));
-  EXPECT_TRUE(DB.getProjectInfo(File));
+  EXPECT_FALSE(DB.getProjectInfo(File));
 }
 
+TEST_F(OverlayCDBTest, GetProjectInfo) {
+  OverlayCDB DB(Base.get());
+  Path File = testPath("foo.cc");
+  Path Header = testPath("foo.h");
+
+  EXPECT_EQ(DB.getProjectInfo(File)->SourceRoot, testRoot());
+  EXPECT_EQ(DB.getProjectInfo(Header)->SourceRoot, testRoot());
+
+  // Shouldn't change after an override.
+  DB.setCompileCommand(File, tooling::CompileCommand());
+  EXPECT_EQ(DB.getProjectInfo(File)->SourceRoot, testRoot());
+  EXPECT_EQ(DB.getProjectInfo(Header)->SourceRoot, testRoot());
+}
 } // namespace
 } // namespace clangd
 } // namespace clang