diff --git a/screw_drive.scad b/screw_drive.scad
index 67b6213..adf9522 100644
--- a/screw_drive.scad
+++ b/screw_drive.scad
@@ -8,6 +8,8 @@
 // FileSummary: Masks for Phillips, Torx and square (Robertson) driver holes.
 //////////////////////////////////////////////////////////////////////
 
+BOSL2_SCREW_DRIVED = is_undef(_BOSL2_STD) && (is_undef(BOSL2_NO_STD_WARNING) || !BOSL2_NO_STD_WARNING) ?
+       echo("Warning: screw_drive.scad included without std.scad; dependencies may be missing\nSet BOSL2_NO_STD_WARNING = true to mute this warning.") true : true;
 
 include <structs.scad>