diff --git a/code/game/dna/dna_modifier.dm b/code/game/dna/dna_modifier.dm
index cfd86f5133a..1c38792e544 100644
--- a/code/game/dna/dna_modifier.dm
+++ b/code/game/dna/dna_modifier.dm
@@ -926,7 +926,7 @@
 			return 1
 
 		if (bufferOption == "createInjector")
-			if (src.injector_ready || waiting_for_user_input)
+			if(injector_ready && !waiting_for_user_input)
 
 				var/success = 1
 				var/obj/item/weapon/dnainjector/I = new /obj/item/weapon/dnainjector
@@ -938,11 +938,11 @@
 						selectedbuf=buf.dna.SE
 					else
 						selectedbuf=buf.dna.UI
-					var/blk = input(usr,"Select Block","Block") in all_dna_blocks(selectedbuf)
+					var/blk = input(usr,"Select Block","Block") as null|anything in all_dna_blocks(selectedbuf)
 					success = setInjectorBlock(I,blk,buf)
 				else
 					I.buf = buf.copy()
-				waiting_for_user_input=0
+				waiting_for_user_input = 0
 				if(success)
 					I.forceMove(src.loc)
 					I.name += " ([buf.name])"