diff --git a/code/controllers/subsystem/parallax.dm b/code/controllers/subsystem/parallax.dm
index 9135f62b03f..1e3c8aca0d9 100644
--- a/code/controllers/subsystem/parallax.dm
+++ b/code/controllers/subsystem/parallax.dm
@@ -34,7 +34,7 @@ SUBSYSTEM_DEF(parallax)
 		for (A; isloc(A.loc) && !isturf(A.loc); A = A.loc);
 
 		if(A != C.movingmob)
-			if(C.movingmob != null)
+			if(C.movingmob != null && C.movingmob.client_mobs_in_contents)
 				C.movingmob.client_mobs_in_contents -= C.mob
 				UNSETEMPTY(C.movingmob.client_mobs_in_contents)
 			LAZYINITLIST(A.client_mobs_in_contents)