diff --git a/docs/install.rst b/docs/install.rst
index ac262de..231399e 100644
--- a/docs/install.rst
+++ b/docs/install.rst
@@ -13,6 +13,7 @@ Installation needs Python, pip and virtualenv::
 
 Gallery building needs graphicsmagick library::
 
+    # graphicsmagick need to have a version of gcc-5-base in 5.3.1
     apt-get install graphicsmagick
 
 An video convertor like ffmpeg::