diff --git a/tools/aapt2/Debug.cpp b/tools/aapt2/Debug.cpp
index f064cb1..e0d7abe 100644
--- a/tools/aapt2/Debug.cpp
+++ b/tools/aapt2/Debug.cpp
@@ -414,7 +414,7 @@
  public:
   using xml::ConstVisitor::Visit;
 
-  XmlPrinter(Printer* printer) : printer_(printer) {
+  explicit XmlPrinter(Printer* printer) : printer_(printer) {
   }
 
   void Visit(const xml::Element* el) override {