diff --git a/src/addons/lua_engine.cpp b/src/addons/lua_engine.cpp
index 5e5b2f1f..55543d4e 100644
--- a/src/addons/lua_engine.cpp
+++ b/src/addons/lua_engine.cpp
@@ -1397,6 +1397,10 @@ void LuaEngine::registerCoreAPI() {
         "function mt:GetHorizontalScrollRange() return 0 end\n"
         "function mt:GetVerticalScroll() return 0 end\n"
         "function mt:GetHorizontalScroll() return 0 end\n"
+        // Zero when unset, which is what the real client answers and what
+        // FrameXML concatenates into a name without checking.
+        "function mt:SetID(id) self.__id = id end\n"
+        "function mt:GetID() return self.__id or 0 end\n"
         "function mt:SetScrollChild(child) self.__scrollChild = child end\n"
         "function mt:GetScrollChild() return self.__scrollChild end\n"
         "function mt:SetFontString(fs) self.__fontString = fs end\n"
diff --git a/src/ui/framexml_emitter.cpp b/src/ui/framexml_emitter.cpp
index efa062a5..19417fdf 100644
--- a/src/ui/framexml_emitter.cpp
+++ b/src/ui/framexml_emitter.cpp
@@ -408,6 +408,14 @@ struct Emitter {
         if (const std::string* strata = node.attr("frameStrata")) {
             line(var + ":SetFrameStrata(" + quote(*strata) + ")");
         }
+        // How a frame in a numbered set knows which one it is, and FrameXML
+        // builds names out of it: PartyMemberFrame_RefreshPetDebuffs reaches
+        // for _G["PartyMemberFrame" .. self:GetID() .. "PetFrame"]. Ignoring
+        // the attribute left every one of the 848 declared across 57 files
+        // answering zero.
+        if (const std::string* id = node.attr("id"); id && !id->empty()) {
+            line(var + ":SetID(" + *id + ")");
+        }
         if (node.attr("enableMouse")) {
             line(var + ":EnableMouse(" + (node.attrBool("enableMouse") ? "true" : "false") + ")");
         }
diff --git a/tests/test_framexml.cpp b/tests/test_framexml.cpp
index 87c273d0..4ef9999d 100644
--- a/tests/test_framexml.cpp
+++ b/tests/test_framexml.cpp
@@ -229,6 +229,15 @@ TEST_CASE("A template installs OnLoad but does not run it", "[framexml][emit]")
     REQUIRE(has(r.lua, "SetScript(\"OnLoad\""));
 }
 
+TEST_CASE("A frame's id becomes SetID", "[framexml][emit]") {
+    // How a frame in a numbered set knows which one it is. FrameXML builds
+    // names out of it — PartyMemberFrame_RefreshPetDebuffs reaches for
+    // _G["PartyMemberFrame" .. self:GetID() .. "PetFrame"] — and 848 of these
+    // are declared across 57 files.
+    XmlNode root = parseOrFail("<Ui><Frame name=\"F\" id=\"3\"/></Ui>");
+    REQUIRE(has(emitFrameXml(root).lua, ":SetID(3)"));
+}
+
 TEST_CASE("parentKey binds a region to a field on its owner", "[framexml][emit]") {
     // How FrameXML's handlers reach their own pieces: QuestHonorFrameTemplate's
     // OnLoad opens with self.icon:SetTexture(...), and the icon is bound only