diff --git a/taglib/mp4/mp4file.cpp b/taglib/mp4/mp4file.cpp
index bcb88afa..3165256c 100644
--- a/taglib/mp4/mp4file.cpp
+++ b/taglib/mp4/mp4file.cpp
@@ -40,7 +40,7 @@ using namespace TagLib;
 class MP4::File::FilePrivate
 {
 public:
-  FilePrivate() : tag(0), atoms(0)
+  FilePrivate() : tag(0), atoms(0), properties(0)
   {
   }