diff --git a/doc/doxygen/Doxyfile b/doc/doxygen/Doxyfile
index 83af7c02f..689fdc82f 100644
--- a/doc/doxygen/Doxyfile
+++ b/doc/doxygen/Doxyfile
@@ -611,7 +611,7 @@ RECURSIVE              = YES
 # excluded from the INPUT source files. This way you can easily exclude a
 # subdirectory from a directory tree whose root is specified with the INPUT tag.
 
-EXCLUDE                =
+EXCLUDE                = include/cantera/ext
 
 # The EXCLUDE_SYMLINKS tag can be used select whether or not files or
 # directories that are symbolic links (a Unix filesystem feature) are excluded