diff --git a/library/include/DataDefs.h b/library/include/DataDefs.h
index 61d5dec41..0966c7f31 100644
--- a/library/include/DataDefs.h
+++ b/library/include/DataDefs.h
@@ -707,6 +707,9 @@ namespace DFHack {
 // Global object pointers
 #include "df/global_objects.h"
 
+#define DF_GLOBAL_VALUE(name,defval) (df::global::name ? *df::global::name : defval)
+#define DF_GLOBAL_FIELD(name,fname,defval) (df::global::name ? df::global::name->fname : defval)
+
 // A couple of headers that have to be included at once
 #include "df/coord2d.h"
 #include "df/coord.h"
diff --git a/plugins/siege-engine.cpp b/plugins/siege-engine.cpp
index 2e362afec..7c880351e 100644
--- a/plugins/siege-engine.cpp
+++ b/plugins/siege-engine.cpp
@@ -1573,6 +1573,8 @@ struct projectile_hook : df::proj_itemst {
         if (next_pos.z == cur_pos.z && !isPassableTile(next_pos))
             start_z = 49000;
 
+        bool forbid_ammo = DF_GLOBAL_VALUE(standing_orders_forbid_used_ammo, false);
+
         MapExtras::MapCache mc;
         std::vector<df::item*> contents;
         Items::getContainedItems(item, &contents);
@@ -1581,6 +1583,9 @@ struct projectile_hook : df::proj_itemst {
         {
             auto child = contents[i];
 
+            if (forbid_ammo)
+                child->flags.bits.forbid = true;
+
             // Liquids are vaporized so that they cover nearby units
             if (child->isLiquid())
             {