diff --git a/java/app_builder.go b/java/app_builder.go
index 69e462c..b53c15a 100644
--- a/java/app_builder.go
+++ b/java/app_builder.go
@@ -32,7 +32,7 @@
 var (
 	Signapk, SignapkRE = remoteexec.StaticRules(pctx, "signapk",
 		blueprint.RuleParams{
-			Command: `$reTemplate${config.JavaCmd} ${config.JavaVmFlags} -Djava.library.path=$$(dirname ${config.SignapkJniLibrary}) ` +
+			Command: `rm -f $out && $reTemplate${config.JavaCmd} ${config.JavaVmFlags} -Djava.library.path=$$(dirname ${config.SignapkJniLibrary}) ` +
 				`-jar ${config.SignapkCmd} $flags $certificates $in $out`,
 			CommandDeps: []string{"${config.SignapkCmd}", "${config.SignapkJniLibrary}"},
 		},