diff --git a/Doxyfile b/Doxyfile
index dce6bdb72..e24e367ae 100644
--- a/Doxyfile
+++ b/Doxyfile
@@ -349,7 +349,7 @@ OPTIMIZE_OUTPUT_SLICE  = NO
 #
 # Note see also the list of default file extension mappings.
 
-EXTENSION_MAPPING       = proto=C++
+EXTENSION_MAPPING      = proto=C++
 
 # If the MARKDOWN_SUPPORT tag is enabled then Doxygen pre-processes all comments
 # according to the Markdown format, which allows for more readable