diff --git a/src/critter.cc b/src/critter.cc
index 4439eb0..50fa5f3 100644
--- a/src/critter.cc
+++ b/src/critter.cc
@@ -1396,4 +1396,22 @@ bool _critter_flag_check(int pid, int flag)
     return (proto->critter.data.flags & flag) != 0;
 }
 
+// 0x42E6F0
+void critter_flag_set(int pid, int flag)
+{
+    Proto* proto;
+
+    if (pid == -1) {
+        return;
+    }
+
+    if (PID_TYPE(pid) != OBJ_TYPE_CRITTER) {
+        return;
+    }
+
+    protoGetProto(pid, &proto);
+
+    proto->critter.data.flags |= flag;
+}
+
 } // namespace fallout
diff --git a/src/critter.h b/src/critter.h
index 7423834..ea83f8d 100644
--- a/src/critter.h
+++ b/src/critter.h
@@ -70,6 +70,7 @@ int critterGetMovementPointCostAdjustedForCrippledLegs(Object* critter, int a2);
 bool critterIsEncumbered(Object* critter);
 bool critterIsFleeing(Object* a1);
 bool _critter_flag_check(int pid, int flag);
+void critter_flag_set(int pid, int flag);
 
 } // namespace fallout