diff --git a/code/controllers/subsystem/pathfinder.dm b/code/controllers/subsystem/pathfinder.dm
index 0dd3cc39354..a7f99a4c13b 100644
--- a/code/controllers/subsystem/pathfinder.dm
+++ b/code/controllers/subsystem/pathfinder.dm
@@ -29,7 +29,7 @@ SUBSYSTEM_DEF(pathfinder)
 		while(flow[free])
 			CHECK_TICK
 			free = (free % lcount) + 1
-		var/t = addtimer(CALLBACK(src, /datum/flowcache.proc/toolong, free), 150, TIMER_STOPPABLE)
+		var/t = addtimer(CALLBACK(src, TYPE_PROC_REF(/datum/flowcache, toolong), free), 150, TIMER_STOPPABLE)
 		flow[free] = t
 		flow[t] = M
 		return free
diff --git a/code/controllers/subsystem/ticker.dm b/code/controllers/subsystem/ticker.dm
index a174eee7edd..33cec95cdc1 100644
--- a/code/controllers/subsystem/ticker.dm
+++ b/code/controllers/subsystem/ticker.dm
@@ -338,7 +338,7 @@ SUBSYSTEM_DEF(ticker)
 	#endif
 
 	// Do this 10 second after roundstart because of roundstart lag, and make it more visible
-	addtimer(CALLBACK(src, .proc/handle_antagfishing_reporting), 10 SECONDS)
+	addtimer(CALLBACK(src, PROC_REF(handle_antagfishing_reporting)), 10 SECONDS)
 	return TRUE
 
 
diff --git a/code/modules/pda/PDA.dm b/code/modules/pda/PDA.dm
index 1ca786c69b9..30836268fcc 100644
--- a/code/modules/pda/PDA.dm
+++ b/code/modules/pda/PDA.dm
@@ -306,7 +306,7 @@ GLOBAL_LIST_EMPTY(PDAs)
 /obj/item/pda/proc/add_pen(obj/item/P)
 	P.forceMove(src)
 	held_pen = P
-	RegisterSignal(held_pen, COMSIG_PARENT_QDELETING, .proc/clear_pen)
+	RegisterSignal(held_pen, COMSIG_PARENT_QDELETING, PROC_REF(clear_pen))
 
 /obj/item/pda/proc/clear_pen()
 	UnregisterSignal(held_pen, COMSIG_PARENT_QDELETING)
diff --git a/tools/ci/check_grep.sh b/tools/ci/check_grep.sh
index b34715bc5c8..12b6b99475d 100755
--- a/tools/ci/check_grep.sh
+++ b/tools/ci/check_grep.sh
@@ -40,6 +40,11 @@ if grep -P '/obj/merge_conflict_marker' _maps/**/*.dmm; then
     echo "ERROR: Merge conflict markers detected in map, please resolve all merge failures!"
     st=1
 fi;
+# Check for non-515 compatable .proc/ syntax
+if grep -P --exclude='__byond_version_compat.dm' '\.proc/' code/**/*.dm; then
+    echo "ERROR: Outdated proc reference use detected in code, please use proc reference helpers."
+    st=1
+fi;
 nl='
 '
 nl=$'\n'