diff --git a/include/macros.h b/include/macros.h
index 9246d0b..234a694 100644
--- a/include/macros.h
+++ b/include/macros.h
@@ -195,7 +195,7 @@ static_assert_eq(bswap(bswap(128lu)), 128, "bswap128 (lu) failed (3)");
 
 #define FATAL(msg, ...) (TRACEx(FATAL, "FATAL",   msg, ## __VA_ARGS__), abort())
 
-#define TODO(x) FATAL("function %s() is unimplemented: " x, __func__)
+#define TODO(x, ...) FATAL("function %s() is unimplemented: " x, __func__, ## __VA_ARGS__)
 
 //  Debug testing
 
diff --git a/src/display.c b/src/display.c
index 104bc00..ee81724 100644
--- a/src/display.c
+++ b/src/display.c
@@ -45,6 +45,7 @@ void display_result(FILE* output, dispin_t input, dispkind_t how, dispflags_t fl
 		case DISPK_CSV:
 		case DISPK_BINARY:
 		case DISPK_INI:
-		default: COLD_EXPR(FATAL("unknown or unimplemented display kind: %d", (int)how));
+			TODO("display kind %d is unimplemented", (int)how);
+		default: COLD_EXPR(FATAL("unknown display kind: %d", (int)how));
 	}
 }