diff --git a/java/builder.go b/java/builder.go
index 6912c87..e359529 100644
--- a/java/builder.go
+++ b/java/builder.go
@@ -21,9 +21,10 @@
 import (
 	"strings"
 
-	"android/soong/android"
-
 	"github.com/google/blueprint"
+
+	"android/soong/android"
+	"android/soong/java/config"
 )
 
 var (
@@ -166,6 +167,11 @@
 func RunErrorProne(ctx android.ModuleContext, srcFiles android.Paths, srcFileLists android.Paths,
 	flags javaBuilderFlags, deps android.Paths) android.Path {
 
+	if config.ErrorProneJar == "" {
+		ctx.ModuleErrorf("cannot build with Error Prone, missing external/error_prone?")
+		return nil
+	}
+
 	classDir := android.PathForModuleOut(ctx, "classes-errorprone")
 	annoDir := android.PathForModuleOut(ctx, "anno-errorprone")
 	classFileList := android.PathForModuleOut(ctx, "classes-errorprone.list")