diff --git a/taglib/fileref.cpp b/taglib/fileref.cpp
index 12abc83d..306a8cd2 100644
--- a/taglib/fileref.cpp
+++ b/taglib/fileref.cpp
@@ -86,8 +86,8 @@ namespace
 
 #endif
 
-      const int pos = s.rfind(".");
-      if(pos != -1)
+      const size_t pos = s.rfind(".");
+      if(pos != String::npos)
         ext = s.substr(pos + 1).upper();
     }