diff --git a/cc/config/tidy.go b/cc/config/tidy.go
index 7cc9f43..7c20dd5 100644
--- a/cc/config/tidy.go
+++ b/cc/config/tidy.go
@@ -87,27 +87,11 @@
 		}, ",")
 	})
 
-	// Give warnings to header files only in selected directories.
-	// Do not give warnings to external or vendor header files, which contain too
-	// many warnings.
+	// To reduce duplicate warnings from the same header files,
+	// header-filter will contain only the module directory and
+	// those specified by DEFAULT_TIDY_HEADER_DIRS.
 	pctx.VariableFunc("TidyDefaultHeaderDirs", func(ctx android.PackageVarContext) string {
-		if override := ctx.Config().Getenv("DEFAULT_TIDY_HEADER_DIRS"); override != "" {
-			return override
-		}
-		return strings.Join([]string{
-			"art/",
-			"bionic/",
-			"bootable/",
-			"build/",
-			"cts/",
-			"dalvik/",
-			"developers/",
-			"development/",
-			"frameworks/",
-			"libcore/",
-			"libnativehelper/",
-			"system/",
-		}, "|")
+		return ctx.Config().Getenv("DEFAULT_TIDY_HEADER_DIRS")
 	})
 
 	// Use WTIH_TIDY_FLAGS to pass extra global default clang-tidy flags.
diff --git a/cc/tidy.go b/cc/tidy.go
index 972ad7b..251c67b 100644
--- a/cc/tidy.go
+++ b/cc/tidy.go
@@ -20,6 +20,7 @@
 
 	"github.com/google/blueprint/proptools"
 
+	"android/soong/android"
 	"android/soong/cc/config"
 )
 
@@ -75,9 +76,17 @@
 	}
 	esc := proptools.NinjaAndShellEscapeList
 	flags.TidyFlags = append(flags.TidyFlags, esc(tidy.Properties.Tidy_flags)...)
-	// If TidyFlags is empty, add default header filter.
-	if len(flags.TidyFlags) == 0 {
-		headerFilter := "-header-filter=\"(" + ctx.ModuleDir() + "|${config.TidyDefaultHeaderDirs})\""
+	// If TidyFlags does not contain -header-filter, add default header filter.
+	// Find the substring because the flag could also appear as --header-filter=...
+	// and with or without single or double quotes.
+	if !android.SubstringInList(flags.TidyFlags, "-header-filter=") {
+		defaultDirs := ctx.Config().Getenv("DEFAULT_TIDY_HEADER_DIRS")
+		headerFilter := "-header-filter="
+		if defaultDirs == "" {
+			headerFilter += ctx.ModuleDir() + "/"
+		} else {
+			headerFilter += "\"(" + ctx.ModuleDir() + "/|" + defaultDirs + ")\""
+		}
 		flags.TidyFlags = append(flags.TidyFlags, headerFilter)
 	}