diff --git a/trigonometry.scad b/trigonometry.scad
index d872f35..8aa49c5 100644
--- a/trigonometry.scad
+++ b/trigonometry.scad
@@ -9,6 +9,8 @@
 // FileFootnotes: STD=Included in std.scad
 //////////////////////////////////////////////////////////////////////
 
+_BOSL2_TRIGONOMETRY = is_undef(_BOSL2_STD) && (is_undef(BOSL2_NO_STD_WARNING) || !BOSL2_NO_STD_WARNING) ?
+       echo("Warning: triginometry.scad included without std.scad; dependencies may be missing\nSet BOSL2_NO_STD_WARNING = true to mute this warning.") true : true;
 
 
 // Section: 2D General Triangle Functions