diff --git a/panda/src/pnmimage/pnmImageHeader.I b/panda/src/pnmimage/pnmImageHeader.I
index ab03cbdaec..a92ee9bb7d 100644
--- a/panda/src/pnmimage/pnmImageHeader.I
+++ b/panda/src/pnmimage/pnmImageHeader.I
@@ -189,3 +189,18 @@ INLINE PNMFileType *PNMImageHeader::
 get_type() const {
   return _type;
 }
+
+////////////////////////////////////////////////////////////////////
+//     Function: PNMImageHeader::set_type
+//       Access: Public
+//  Description: Sets the file type of this PNMImage.  This will be
+//               the default type used when an image is read, if the
+//               type cannot be determined by magic number or inferred
+//               by extension, or the type used when the image is
+//               written, if the type cannot be inferred from the
+//               filename extension.
+////////////////////////////////////////////////////////////////////
+INLINE void PNMImageHeader::
+set_type(PNMFileType *type) {
+  _type = type;
+}
diff --git a/panda/src/pnmimage/pnmImageHeader.h b/panda/src/pnmimage/pnmImageHeader.h
index 6e1eea07da..96d871c209 100644
--- a/panda/src/pnmimage/pnmImageHeader.h
+++ b/panda/src/pnmimage/pnmImageHeader.h
@@ -61,6 +61,7 @@ public:
 
   INLINE bool has_type() const;
   INLINE PNMFileType *get_type() const;
+  INLINE void set_type(PNMFileType *type);
 
   bool read_header(const Filename &filename, PNMFileType *type = NULL);