diff --git a/doc/Doxyfile.in b/doc/Doxyfile.in
index 091ce5639..a0c8f73fa 100644
--- a/doc/Doxyfile.in
+++ b/doc/Doxyfile.in
@@ -1189,7 +1189,7 @@ SEARCH_INCLUDES        = YES
 # contain include files that are not input files but should be processed by
 # the preprocessor.
 
-INCLUDE_PATH           =
+INCLUDE_PATH           = "${Eigen_SOURCE_DIR}/Eigen/src/plugins" 
 
 # You can use the INCLUDE_FILE_PATTERNS tag to specify one or more wildcard
 # patterns (like *.h and *.hpp) to filter out the header-files in the