diff --git a/android/writedocs.go b/android/writedocs.go
index 91c2318..6417690 100644
--- a/android/writedocs.go
+++ b/android/writedocs.go
@@ -34,7 +34,8 @@
 type docsSingleton struct{}
 
 func primaryBuilderPath(ctx SingletonContext) Path {
-	primaryBuilder, err := filepath.Rel(ctx.Config().BuildDir(), os.Args[0])
+	buildDir := absolutePath(ctx.Config().BuildDir())
+	primaryBuilder, err := filepath.Rel(buildDir, os.Args[0])
 	if err != nil {
 		ctx.Errorf("path to primary builder %q is not in build dir %q",
 			os.Args[0], ctx.Config().BuildDir())