diff --git a/code/__DEFINES/maths.dm b/code/__DEFINES/maths.dm
index b4de855bef9..cd75a7a0172 100644
--- a/code/__DEFINES/maths.dm
+++ b/code/__DEFINES/maths.dm
@@ -117,7 +117,8 @@
 #define TORADIANS(degrees) ((degrees) * 0.0174532925)
 
 /// Gets shift x that would be required the bitflag (1<<x)
-#define TOBITSHIFT(bit) ( log(2, bit) )
+/// We need the round because log has floating-point inaccuracy, and if we undershoot at all on list indexing we'll get the wrong index.
+#define TOBITSHIFT(bit) ( round(log(2, bit), 1) )
 
 // Will filter out extra rotations and negative rotations
 // E.g: 540 becomes 180. -180 becomes 180.