diff --git a/sourcedoc/Doxyfile.in b/sourcedoc/Doxyfile.in
index 16f78f9882..097d4a9aab 100644
--- a/sourcedoc/Doxyfile.in
+++ b/sourcedoc/Doxyfile.in
@@ -838,7 +838,7 @@ GRAPHICAL_HIERARCHY    = YES
 # generated by dot. Possible values are gif, jpg, and png
 # If left blank gif will be used.
 
-DOT_IMAGE_FORMAT       = gif
+DOT_IMAGE_FORMAT       = png
 
 # The tag DOT_PATH can be used to specify the path where the dot tool can be 
 # found. If left blank, it is assumed the dot tool can be found on the path.