diff --git a/eo/acinclude.m4 b/eo/acinclude.m4
index 4e8e0093..af837ca6 100644
--- a/eo/acinclude.m4
+++ b/eo/acinclude.m4
@@ -32,7 +32,7 @@ AC_DEFUN([AC_GNUPLOT], [dnl
                    [ac_cv_use_gnuplot=no])
     if test "$ac_cv_use_gnuplot" = "yes"; then
         AC_ARG_VAR([GNUPLOT], [gnuplot used for graphical display])
-        AC_CHECK_PROG([GNUPLOT], [gnuplot], [true])
+        AC_CHECK_PROG([GNUPLOT], [gnuplot], [gnuplot], [true])
         AC_DEFINE([HAVE_GNUPLOT], [1], [gnuplot graphical display])
     else
         AC_DEFINE([NO_GNUPLOT], [1], [no gnuplot graphical display])
diff --git a/eo/src/utils/eoGnuplot.h b/eo/src/utils/eoGnuplot.h
index adee033b..e057900a 100644
--- a/eo/src/utils/eoGnuplot.h
+++ b/eo/src/utils/eoGnuplot.h
@@ -42,7 +42,7 @@ public:
     /** Open pipe to Gnuplot.
 
     @param _title Title for gnuplot window.
-    @param _extra Extra parameters to gnuplot.
+    @param _extra Extra parameters to gnuplot (default <none>).
     */
     eoGnuplot(std::string _title, std::string _extra = std::string(""));