diff --git a/clang-tools-extra/clangd/Preamble.cpp b/clang-tools-extra/clangd/Preamble.cpp
--- a/clang-tools-extra/clangd/Preamble.cpp
+++ b/clang-tools-extra/clangd/Preamble.cpp
@@ -696,6 +696,10 @@
       Patch << llvm::formatv(
           "#{0} {1}\n", spellingForIncDirective(Inc.Directive), Inc.Written);
     }
+  } else {
+    // Includes haven't changed or we're not patching.
+    // So, copy them over from the baseline.
+    PP.PreambleIncludes = Baseline.Includes.MainFileIncludes;
   }
 
   if (DirectivesChanged) {
diff --git a/clang-tools-extra/clangd/unittests/PreambleTests.cpp b/clang-tools-extra/clangd/unittests/PreambleTests.cpp
--- a/clang-tools-extra/clangd/unittests/PreambleTests.cpp
+++ b/clang-tools-extra/clangd/unittests/PreambleTests.cpp
@@ -225,6 +225,20 @@
       .str();
 }
 
+TEST(PreamblePatchTest, IncludesArePreserved) {
+  llvm::StringLiteral Baseline = "//error-ok\n#include <foo>\n#include <bar>\n";
+  auto Modified = Baseline + "#define FOO\n";
+
+  auto Includes = createPatchedAST(Baseline, Modified.str())
+                      ->getIncludeStructure()
+                      .MainFileIncludes;
+  EXPECT_TRUE(!Includes.empty());
+  EXPECT_EQ(Includes, TestTU::withCode(Baseline)
+                          .build()
+                          .getIncludeStructure()
+                          .MainFileIncludes);
+}
+
 TEST(PreamblePatchTest, Define) {
   // BAR should be defined while parsing the AST.
   struct {