diff --git a/code/modules/research/protolathe.dm b/code/modules/research/protolathe.dm
index 09a2b9a7974..beeacb6286d 100644
--- a/code/modules/research/protolathe.dm
+++ b/code/modules/research/protolathe.dm
@@ -199,8 +199,9 @@ Note: Must be placed west/left of and R&D console to function.
 	src.updateUsrDialog()
 
 	if(stack)
-		src.overlays += "protolathe_[stack.name]"
+		var/stackname = stack.name
+		src.overlays += "protolathe_[stackname]"
 		sleep(10)
-		src.overlays -= "protolathe_[stack.name]"
+		src.overlays -= "protolathe_[stackname]"
 
 	return