diff --git a/admin/scons/Platform.py b/admin/scons/Platform.py
index 2a5931417..c74b8e39c 100644
--- a/admin/scons/Platform.py
+++ b/admin/scons/Platform.py
@@ -129,6 +129,7 @@ def configure(env):
         problems.append('Xlib.h and Xutil.h required. Please install libx11-dev.')
     
     if not conf.CheckPkgConfig('xv')  : problems.append('Need libXv...')
+    if not conf.CheckPkgConfig('x11') : problems.append('Need X-lib...')   # for the xvdisplayer widget
     if not conf.CheckPkgConfig('xext'): problems.append('Need libXext.')
     
     
diff --git a/doc/technical/build/Dependencies.txt b/doc/technical/build/Dependencies.txt
index 1b7b0262c..967ac6bbd 100644
--- a/doc/technical/build/Dependencies.txt
+++ b/doc/technical/build/Dependencies.txt
@@ -90,7 +90,7 @@ Libraries
  - libgtkmm-2.4-dev
  - libcairomm-1.0-dev
  - libglibmm-2.4-dev, requiring glib2.0 and gthread-2.0
- - libxv-dev
+ - libxv-dev and X-lib footnote:[for the XV viewer widget `gui/output/xvdisplayer.cpp`]
  - librsvg-2.0 and librsvg2-dev for rendering Icons
  - libgdl-1-dev -- old version of the Gnome Docking Library footnote:[GDL isn't directly related to GNOME any more.
    We contributed to the improvement of this library in the past. These improvements went upstream