diff --git a/Makefile b/Makefile
index 7aed642..ddd27e5 100644
--- a/Makefile
+++ b/Makefile
@@ -70,7 +70,7 @@ doc: | doc-pdf doc-info doc-plain doc-html
 
 # doc images
 doc/img/%.png: doc/img/%.dia
-	dia -e $@ -s 600x $<
+	dia -e $@ -s 300x $<
 
 # doc pdf
 $(PATH_DOC_OUTPUT)/%.pdf: $(doc_src) | mkbuild-doc doc-img
diff --git a/doc/classes.texi b/doc/classes.texi
index ecbdd5a..94b58b5 100644
--- a/doc/classes.texi
+++ b/doc/classes.texi
@@ -302,7 +302,7 @@ and the child is called the @dfn{subtype}. Let's consider the following example,
 where we have a dog, lazy dog, and a dog that walks on two legs:
 
 @float Figure, f:inheritance-ex
-@image{img/inheritance-ex,,,,png}
+@image{img/inheritance-ex}
 @caption{Basic inheritance example}
 @end float