diff --git a/android/defs.go b/android/defs.go
index 38ecb05..1a76721 100644
--- a/android/defs.go
+++ b/android/defs.go
@@ -57,6 +57,15 @@
 		},
 		"cpFlags")
 
+	// A copy rule that only updates the output if it changed.
+	CpIfChanged = pctx.AndroidStaticRule("CpIfChanged",
+		blueprint.RuleParams{
+			Command:     "if ! cmp -s $in $out; then cp $in $out; fi",
+			Description: "cp if changed $out",
+			Restat:      true,
+		},
+		"cpFlags")
+
 	CpExecutable = pctx.AndroidStaticRule("CpExecutable",
 		blueprint.RuleParams{
 			Command:     "rm -f $out && cp $cpPreserveSymlinks $cpFlags $in $out && chmod +x $out",
diff --git a/java/lint.go b/java/lint.go
index af83664..12e4129 100644
--- a/java/lint.go
+++ b/java/lint.go
@@ -437,13 +437,13 @@
 	}
 
 	ctx.Build(pctx, android.BuildParams{
-		Rule:   android.Cp,
+		Rule:   android.CpIfChanged,
 		Input:  android.OutputFileForModule(ctx, frameworkDocStubs, ".annotations.zip"),
 		Output: copiedAnnotationsZipPath(ctx),
 	})
 
 	ctx.Build(pctx, android.BuildParams{
-		Rule:   android.Cp,
+		Rule:   android.CpIfChanged,
 		Input:  android.OutputFileForModule(ctx, frameworkDocStubs, ".api_versions.xml"),
 		Output: copiedAPIVersionsXmlPath(ctx),
 	})