diff --git a/src/main.cpp b/src/main.cpp
index 961cb2b..31a404a 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -441,7 +441,10 @@ static void Shutdown(SDL_Window* window, SDL_GLContext gl_context);
 
 // Global single instance lock. Keyed PER VARIANT so the full node and Lite can run side by side —
 // their config dirs are already separate (DRAGONX_APP_NAME), so only this lock kept them apart.
-#ifdef DRAGONX_LITE_BUILD
+// NB: DRAGONX_LITE_BUILD is ALWAYS defined (0 for the full node, 1 for Lite) via $<BOOL:...>, so this
+// must be #if (value), not #ifdef (existence) — #ifdef is true for both and made the full node grab
+// the Lite lock.
+#if DRAGONX_LITE_BUILD
 static dragonx::util::SingleInstance g_single_instance("obsidiandragonlite");
 #else
 static dragonx::util::SingleInstance g_single_instance("obsidiandragon");