diff --git a/dtool/src/dtoolutil/filename.I b/dtool/src/dtoolutil/filename.I
index b23947320f..56ba90d838 100644
--- a/dtool/src/dtoolutil/filename.I
+++ b/dtool/src/dtoolutil/filename.I
@@ -608,7 +608,7 @@ compare_to(const Filename &other) const {
  * instead.
  */
 INLINE bool Filename::
-__nonzero__() const {
+__bool__() const {
   return !_filename.empty();
 }
 
diff --git a/dtool/src/dtoolutil/filename.h b/dtool/src/dtoolutil/filename.h
index 66b38356a6..db0728f95c 100644
--- a/dtool/src/dtoolutil/filename.h
+++ b/dtool/src/dtoolutil/filename.h
@@ -232,7 +232,7 @@ PUBLISHED:
   INLINE bool operator != (const std::string &other) const;
   INLINE bool operator < (const std::string &other) const;
   INLINE int compare_to(const Filename &other) const;
-  INLINE bool __nonzero__() const;
+  INLINE bool __bool__() const;
   int get_hash() const;
 
   INLINE void output(std::ostream &out) const;