diff --git a/src/input/Tag.h b/src/input/Tag.h
index c9e997f8e9..78dd65676f 100644
--- a/src/input/Tag.h
+++ b/src/input/Tag.h
@@ -42,11 +42,8 @@ public:
 	/**
 	 * Returns false if the tag represents an error value rather than a
 	 * legal reader type.
-	 * TODO: make this conversion operator "explicit" (C++11) or use a
-	 *       "safe bool" idiom (not necessary if "explicit" is available),
-	 *       otherwise this may allow nonsense/undesired comparison operations.
 	 */
-	operator bool() const	{ return *this != Tag(); }
+	explicit operator bool() const	{ return *this != Tag(); }
 
 	/**
 	 * Assignment operator.
diff --git a/src/logging/Tag.h b/src/logging/Tag.h
index ae75487664..bcb7af946b 100644
--- a/src/logging/Tag.h
+++ b/src/logging/Tag.h
@@ -42,11 +42,8 @@ public:
 	/**
 	 * Returns false if the tag represents an error value rather than a
 	 * legal writer type.
-	 * TODO: make this conversion operator "explicit" (C++11) or use a
-	 *       "safe bool" idiom (not necessary if "explicit" is available),
-	 *       otherwise this may allow nonsense/undesired comparison operations.
 	 */
-	operator bool() const	{ return *this != Tag(); }
+	explicit operator bool() const	{ return *this != Tag(); }
 
 	/**
 	 * Assignment operator.