diff --git a/src/check_asm_cfg.cpp b/src/check_asm_cfg.cpp
index 1f37ccb3d..b866e1b56 100644
--- a/src/check_asm_cfg.cpp
+++ b/src/check_asm_cfg.cpp
@@ -554,6 +554,9 @@ gb_internal void check_asm_cfg_analyse(AsmCtx *asm_ctx, AsmCfg *cfg, CheckerCont
 				if (ed.tie >= 0 || ed.no_init) {
 					continue;
 				}
+				if (ed.pin_flag.len != 0) {
+					continue; // flag-pinned output: defined by a flags side effect, not a reg/param write
+				}
 
 				bool written = false;
 				u16 bit = cfg->decl_pin_bit[i];