diff --git a/session_utils/README b/session_utils/README
index 1fa563acc0..cbe5c44e91 100644
--- a/session_utils/README
+++ b/session_utils/README
@@ -22,8 +22,9 @@ One C++ source per tool, see "example.cc" and "export.cc"
   ./waf
 
 The tool is automatically compiled and deployed when installing, using the
-program-name as prefix.  e.g.  "export.cc" becomes "ardour4-export".
-(or "mixbus3-export", depending on the project configuration)
+program-name as prefix.  e.g.  "export.cc" becomes "ardour4-export"
+(or "mixbus3-export", depending on the project configuration).
+Tool names must start with lower-case alphabetic letter [a-z].
 
 
 Test run from the source
diff --git a/session_utils/wscript b/session_utils/wscript
index 753b8ea8ab..7e20cb1d8b 100644
--- a/session_utils/wscript
+++ b/session_utils/wscript
@@ -85,7 +85,7 @@ def build(bld):
 
     pgmprefix = bld.env['PROGRAM_NAME'].lower() + str(bld.env['MAJOR'])
 
-    utils = bld.path.ant_glob('*.cc', excl=['example.cc', 'common.cc'])
+    utils = bld.path.ant_glob('[a-z]*.cc', excl=['example.cc', 'common.cc'])
 
     for util in utils:
         fn = os.path.splitext(os.path.basename(str(util)))[0]