diff --git a/clang-tools-extra/include-cleaner/unittests/AnalysisTest.cpp b/clang-tools-extra/include-cleaner/unittests/AnalysisTest.cpp
--- a/clang-tools-extra/include-cleaner/unittests/AnalysisTest.cpp
+++ b/clang-tools-extra/include-cleaner/unittests/AnalysisTest.cpp
@@ -311,12 +311,9 @@
   Results = {};
   Results.Missing.push_back("\"d.h\"");
   Code = R"cpp(#include "a.h")cpp";
-  // FIXME: this isn't correct, the main-file header d.h should be added before
-  // a.h.
   EXPECT_EQ(fixIncludes(Results, "d.cc", Code, format::getLLVMStyle()),
-R"cpp(#include "a.h"
-#include "d.h"
-)cpp");
+R"cpp(#include "d.h"
+#include "a.h")cpp");
 }
 
 MATCHER_P3(expandedAt, FileID, Offset, SM, "") {
diff --git a/clang/lib/Tooling/Inclusions/HeaderIncludes.cpp b/clang/lib/Tooling/Inclusions/HeaderIncludes.cpp
--- a/clang/lib/Tooling/Inclusions/HeaderIncludes.cpp
+++ b/clang/lib/Tooling/Inclusions/HeaderIncludes.cpp
@@ -335,7 +335,7 @@
   // Only record the offset of current #include if we can insert after it.
   if (CurInclude.R.getOffset() <= MaxInsertOffset) {
     int Priority = Categories.getIncludePriority(
-        CurInclude.Name, /*CheckMainHeader=*/FirstIncludeOffset < 0);
+        CurInclude.Name, /*CheckMainHeader=*/true);
     CategoryEndOffsets[Priority] = NextLineOffset;
     IncludesByPriority[Priority].push_back(&CurInclude);
     if (FirstIncludeOffset < 0)
@@ -362,7 +362,7 @@
       std::string(llvm::formatv(IsAngled ? "<{0}>" : "\"{0}\"", IncludeName));
   StringRef QuotedName = Quoted;
   int Priority = Categories.getIncludePriority(
-      QuotedName, /*CheckMainHeader=*/FirstIncludeOffset < 0);
+      QuotedName, /*CheckMainHeader=*/true);
   auto CatOffset = CategoryEndOffsets.find(Priority);
   assert(CatOffset != CategoryEndOffsets.end());
   unsigned InsertOffset = CatOffset->second; // Fall back offset
diff --git a/clang/unittests/Tooling/HeaderIncludesTest.cpp b/clang/unittests/Tooling/HeaderIncludesTest.cpp
--- a/clang/unittests/Tooling/HeaderIncludesTest.cpp
+++ b/clang/unittests/Tooling/HeaderIncludesTest.cpp
@@ -143,6 +143,17 @@
   EXPECT_NE(Expected, insert(Code, "<a>")) << "Not main header";
 }
 
+TEST_F(HeaderIncludesTest, InsertMainHeader) {
+  std::string Code = R"cpp(#include "a.h")cpp";
+  std::string Expected = R"cpp(#include "fix.h"
+#include "a.h")cpp";
+
+  Style = format::getGoogleStyle(format::FormatStyle::LanguageKind::LK_Cpp)
+              .IncludeStyle;
+  FileName = "fix.cpp";
+  EXPECT_EQ(Expected, insert(Code, "\"fix.h\""));
+}
+
 TEST_F(HeaderIncludesTest, InsertBeforeSystemHeaderLLVM) {
   std::string Code = "#include <memory>\n"
                      "\n"