diff --git a/src/sfall_opcodes.cc b/src/sfall_opcodes.cc
index 50e7d59..d746f93 100644
--- a/src/sfall_opcodes.cc
+++ b/src/sfall_opcodes.cc
@@ -163,6 +163,30 @@ static void opGetWeaponAmmoPid(Program* program)
     programStackPushInteger(program, pid);
 }
 
+// There are two problems with this function.
+//
+// 1. Sfall's implementation changes ammo PID of misc items, which is impossible
+// since it's stored in proto, not in the object.
+// 2. Changing weapon's ammo PID is done without checking for ammo
+// quantity/capacity which can probably lead to bad things.
+//
+// set_weapon_ammo_pid
+static void opSetWeaponAmmoPid(Program* program)
+{
+    int ammoTypePid = programStackPopInteger(program);
+    Object* obj = static_cast<Object*>(programStackPopPointer(program));
+
+    if (obj != nullptr) {
+        if (PID_TYPE(obj->pid) == OBJ_TYPE_ITEM) {
+            switch (itemGetType(obj)) {
+            case ITEM_TYPE_WEAPON:
+                obj->data.item.weapon.ammoTypePid = ammoTypePid;
+                break;
+            }
+        }
+    }
+}
+
 // get_weapon_ammo_count
 static void opGetWeaponAmmoCount(Program* program)
 {
@@ -297,6 +321,7 @@ void sfallOpcodesInit()
     interpreterRegisterOpcode(0x8211, opGetVersionMinor);
     interpreterRegisterOpcode(0x8212, opGetVersionPatch);
     interpreterRegisterOpcode(0x8217, opGetWeaponAmmoPid);
+    interpreterRegisterOpcode(0x8218, opSetWeaponAmmoPid);
     interpreterRegisterOpcode(0x8219, opGetWeaponAmmoCount);
     interpreterRegisterOpcode(0x821A, opSetWeaponAmmoCount);
     interpreterRegisterOpcode(0x821C, opGetMouseX);