diff --git a/docs/Doxyfile.in b/docs/Doxyfile.in
index c4d69b6c..f7401245 100644
--- a/docs/Doxyfile.in
+++ b/docs/Doxyfile.in
@@ -820,7 +820,8 @@ WARN_LOGFILE           =
 # Note: If this tag is empty the current directory is searched.
 
 INPUT                  = @CMAKE_SOURCE_DIR@/include \
-                         @CMAKE_SOURCE_DIR@/source
+                         @CMAKE_SOURCE_DIR@/source  \
+                         @CMAKE_SOURCE_DIR@/extras
 
 # This tag can be used to specify the character encoding of the source files
 # that doxygen parses. Internally doxygen uses the UTF-8 encoding. Doxygen uses