diff --git a/SConstruct b/SConstruct
index aa382f2c8..717609d76 100644
--- a/SConstruct
+++ b/SConstruct
@@ -90,7 +90,7 @@ def setupBasicEnvironment(localDefinitions):
     env.Append ( CCCOM=' -std=gnu99') 
     env.Append ( SHCCCOM=' -std=gnu99') # workaround for a bug: CCCOM currently doesn't honour CFLAGS, only CCFLAGS 
     env.Replace( CPPPATH   =["#src"]    # used to find includes, "#" means always absolute to build-root
-               , CPPDEFINES=['-DLUMIERA_VERSION='+VERSION ]     # note: it's a list to append further defines
+               , CPPDEFINES=['LUMIERA_VERSION='+VERSION ]    # note: it's a list to append further defines
                , CCFLAGS='-Wall -Wextra '
                , CFLAGS='-std=gnu99' 
                )
@@ -367,7 +367,7 @@ def defineBuildTargets(env, artifacts):
     envGtk.mergeConf(['gtkmm-2.4','gthread-2.0','cairomm-1.0','gdl','xv','xext','sm'])
     envGtk.Append(LIBS=core)
     
-    objgui  = srcSubtree(envGtk,'src/gui')
+    objgui  = srcSubtree(envGtk,'src/gui', appendCPP='LUMIERA_PLUGIN')
     guimodule = envGtk.LumieraPlugin('gtk_gui', objgui, install=True)
     artifacts['gui'] = ( guimodule
                        + [env.GuiResource(f) for f in env.Glob('src/gui/*.rc')]
diff --git a/admin/scons/Buildhelper.py b/admin/scons/Buildhelper.py
index aed9c07da..69fb3849d 100644
--- a/admin/scons/Buildhelper.py
+++ b/admin/scons/Buildhelper.py
@@ -49,11 +49,12 @@ def isHelpRequest():
 
 
 
-def srcSubtree(env,tree,isShared=True,builder=None, **args):
+def srcSubtree(env,tree,isShared=True,builder=None,appendCPP=None, **args):
     """ convenience wrapper: scans the given subtree, which is
         relative to the current SConscript, find all source files and
         declare them as Static or SharedObjects for compilation
     """
+    if appendCPP: env.Append(CPPDEFINES=appendCPP)
     root = env.subst(tree)  # expand Construction Vars
     if not builder:
         if isShared:
@@ -160,7 +161,7 @@ def createPlugins(env, dir, **kw):
         @return: a list of build nodes defining a plugin for each of these source trees.
     """
     return [env.LumieraPlugin( getDirname(tree) 
-                             , srcSubtree(env, tree)
+                             , srcSubtree(env, tree, appendCPP='LUMIERA_PLUGIN')
                              , **kw
                              )
             for tree in findSrcTrees(dir)
diff --git a/admin/scons/LumieraEnvironment.py b/admin/scons/LumieraEnvironment.py
index 82a89b6ae..28b1eb48f 100644
--- a/admin/scons/LumieraEnvironment.py
+++ b/admin/scons/LumieraEnvironment.py
@@ -185,6 +185,8 @@ class WrappedStandardExeBuilder(SCons.Util.Proxy):
     def __init__(self, originalBuilder):
         SCons.Util.Proxy.__init__ (self, originalBuilder)
     
+    def __nonzero__(self): return True
+    
     def __call__(self, env, target=None, source=None, **kw):
         """ when the builder gets invoked from the SConscript...
             create a clone environment for specific configuration