diff --git a/java/hiddenapi_modular.go b/java/hiddenapi_modular.go
index f5afe5d..8372132 100644
--- a/java/hiddenapi_modular.go
+++ b/java/hiddenapi_modular.go
@@ -261,10 +261,10 @@
 }
 
 func (p *HiddenAPIFlagFileProperties) hiddenAPIFlagFileInfo(ctx android.ModuleContext) hiddenAPIFlagFileInfo {
-	info := hiddenAPIFlagFileInfo{categoryToPaths: map[*hiddenAPIFlagFileCategory]android.Paths{}}
+	info := hiddenAPIFlagFileInfo{FlagFilesByCategory: FlagFilesByCategory{}}
 	for _, category := range hiddenAPIFlagFileCategories {
 		paths := android.PathsForModuleSrc(ctx, category.propertyValueReader(p))
-		info.categoryToPaths[category] = paths
+		info.FlagFilesByCategory[category] = paths
 	}
 	return info
 }
@@ -365,6 +365,24 @@
 	},
 }
 
+// FlagFilesByCategory maps a hiddenAPIFlagFileCategory to the paths to the files in that category.
+type FlagFilesByCategory map[*hiddenAPIFlagFileCategory]android.Paths
+
+// append appends the supplied flags files to the corresponding category in this map.
+func (s FlagFilesByCategory) append(other FlagFilesByCategory) {
+	for _, category := range hiddenAPIFlagFileCategories {
+		s[category] = append(s[category], other[category]...)
+	}
+}
+
+// dedup removes duplicates in the flag files, while maintaining the order in which they were
+// appended.
+func (s FlagFilesByCategory) dedup() {
+	for category, paths := range s {
+		s[category] = android.FirstUniquePaths(paths)
+	}
+}
+
 // hiddenAPIFlagFileInfo contains paths resolved from HiddenAPIFlagFileProperties and also generated
 // by hidden API processing.
 //
@@ -372,9 +390,9 @@
 // for a module to collate the files from the fragments it depends upon. That is why the fields are
 // all Paths even though they are initialized with a single path.
 type hiddenAPIFlagFileInfo struct {
-	// categoryToPaths maps from the flag file category to the paths containing information for that
-	// category.
-	categoryToPaths map[*hiddenAPIFlagFileCategory]android.Paths
+	// FlagFilesByCategory maps from the flag file category to the paths containing information for
+	// that category.
+	FlagFilesByCategory FlagFilesByCategory
 
 	// The paths to the generated stub-flags.csv files.
 	StubFlagsPaths android.Paths
@@ -392,17 +410,6 @@
 	AllFlagsPaths android.Paths
 }
 
-func (i *hiddenAPIFlagFileInfo) append(other hiddenAPIFlagFileInfo) {
-	for _, category := range hiddenAPIFlagFileCategories {
-		i.categoryToPaths[category] = append(i.categoryToPaths[category], other.categoryToPaths[category]...)
-	}
-	i.StubFlagsPaths = append(i.StubFlagsPaths, other.StubFlagsPaths...)
-	i.AnnotationFlagsPaths = append(i.AnnotationFlagsPaths, other.AnnotationFlagsPaths...)
-	i.MetadataPaths = append(i.MetadataPaths, other.MetadataPaths...)
-	i.IndexPaths = append(i.IndexPaths, other.IndexPaths...)
-	i.AllFlagsPaths = append(i.AllFlagsPaths, other.AllFlagsPaths...)
-}
-
 var hiddenAPIFlagFileInfoProvider = blueprint.NewProvider(hiddenAPIFlagFileInfo{})
 
 // pathForValidation creates a path of the same type as the supplied type but with a name of
@@ -428,14 +435,14 @@
 //
 // flagFileInfo is a struct containing paths to files that augment the information provided by
 // the annotationFlags.
-func buildRuleToGenerateHiddenApiFlags(ctx android.BuilderContext, name, desc string, outputPath android.WritablePath, baseFlagsPath android.Path, annotationFlags android.Path, flagFileInfo *hiddenAPIFlagFileInfo) {
+func buildRuleToGenerateHiddenApiFlags(ctx android.BuilderContext, name, desc string, outputPath android.WritablePath, baseFlagsPath android.Path, annotationFlags android.Path, flagFilesByCategory FlagFilesByCategory, allFlagsPaths android.Paths) {
 
 	// The file which is used to record that the flags file is valid.
 	var validFile android.WritablePath
 
 	// If there are flag files that have been generated by fragments on which this depends then use
 	// them to validate the flag file generated by the rules created by this method.
-	if allFlagsPaths := flagFileInfo.AllFlagsPaths; len(allFlagsPaths) > 0 {
+	if len(allFlagsPaths) > 0 {
 		// The flags file generated by the rule created by this method needs to be validated to ensure
 		// that it is consistent with the flag files generated by the individual fragments.
 
@@ -463,7 +470,7 @@
 
 	// Add the options for the different categories of flag files.
 	for _, category := range hiddenAPIFlagFileCategories {
-		paths := flagFileInfo.categoryToPaths[category]
+		paths := flagFilesByCategory[category]
 		for _, path := range paths {
 			category.commandMutator(command, path)
 		}
@@ -530,7 +537,7 @@
 	// Generate the all-flags.csv which are the flags that will, in future, be encoded into the dex
 	// files.
 	outputPath := android.PathForModuleOut(ctx, hiddenApiSubDir, "all-flags.csv")
-	buildRuleToGenerateHiddenApiFlags(ctx, "modularHiddenApiAllFlags", "modular hiddenapi all flags", outputPath, stubFlagsCSV, annotationFlagsCSV, flagFileInfo)
+	buildRuleToGenerateHiddenApiFlags(ctx, "modularHiddenApiAllFlags", "modular hiddenapi all flags", outputPath, stubFlagsCSV, annotationFlagsCSV, flagFileInfo.FlagFilesByCategory, nil)
 
 	// Store the paths in the info for use by other modules and sdk snapshot generation.
 	flagFileInfo.StubFlagsPaths = android.Paths{stubFlagsCSV}