diff --git a/java/bootclasspath_fragment.go b/java/bootclasspath_fragment.go
index 73dcd19..35eb1f0 100644
--- a/java/bootclasspath_fragment.go
+++ b/java/bootclasspath_fragment.go
@@ -933,11 +933,15 @@
 	}
 
 	var deapexerModule android.Module
-	ctx.VisitDirectDeps(func(module android.Module) {
-		tag := ctx.OtherModuleDependencyTag(module)
+	ctx.VisitDirectDeps(func(to android.Module) {
+		tag := ctx.OtherModuleDependencyTag(to)
 		// Save away the `deapexer` module on which this depends, if any.
 		if tag == android.DeapexerTag {
-			deapexerModule = module
+			if deapexerModule != nil {
+				ctx.ModuleErrorf("Ambiguous duplicate deapexer module dependencies %q and %q",
+					deapexerModule.Name(), to.Name())
+			}
+			deapexerModule = to
 		}
 	})