diff --git a/waftools/rootsys.py b/waftools/rootsys.py
index 7b4b244..21cff43 100644
--- a/waftools/rootsys.py
+++ b/waftools/rootsys.py
@@ -18,6 +18,9 @@ def check_root(cfg, mandatory=False):
     instdir = cfg.options.with_root
 
     if instdir and instdir.lower() in ['no','off','false']:
+        if mandatory:
+            raise RuntimeError("ROOT is mandatory but disabled via command line")
+        print ("optional ROOT dependency disabled by command line")
         return
 
     cfg.env.CXXFLAGS += ['-fPIC']
@@ -29,11 +32,10 @@ def check_root(cfg, mandatory=False):
         
     kwargs = dict(path_list=path_list)
 
-
     cfg.find_program('root-config', var='ROOT-CONFIG', mandatory=mandatory, **kwargs)
     if not 'ROOT-CONFIG' in cfg.env:
         if mandatory:
-            raise RuntimeError("root-config not found but required")
+            raise RuntimeError("root-config not found but ROOT required")
         print ("skipping non mandatory ROOT, use --with-root to force")
         return
 
diff --git a/wscript b/wscript
index a9fe90e..7c0ec94 100644
--- a/wscript
+++ b/wscript
@@ -58,11 +58,13 @@ def configure(cfg):
         submodules.remove('dfp')
 
     # Remove WCT packages that happen to have same name as external name
-    for maybe in "root tbb cuda".split():
-        have='have_%s'%maybe
-        if have.upper() not in cfg.env and maybe in submodules:
-            print ('Removing submodule "%s" due to lack of external dependency'%maybe)
-            submodules.remove(maybe)
+    for pkg,ext in dict(root="ROOTSYS", tbb="TBB", cuda="CUDA").items():
+        have='HAVE_'+ext
+        if have in cfg.env:
+            continue
+        if pkg in submodules:
+            print ('Removing package "%s" due to lack of external dependency'%pkg)
+            submodules.remove(pkg)
 
     cfg.env.SUBDIRS = submodules
     print ('Configured for submodules: %s' % (', '.join(submodules), ))