diff --git a/test/tap/tests/fast_forward_grace_close.cpp b/test/tap/tests/fast_forward_grace_close.cpp
index 341c135fe..c88d709d1 100644
--- a/test/tap/tests/fast_forward_grace_close.cpp
+++ b/test/tap/tests/fast_forward_grace_close.cpp
@@ -59,10 +59,16 @@ int main() {
 	MYSQL_QUERY(proxysql_conn, "CREATE DATABASE IF NOT EXISTS test");
 	MYSQL_QUERY(proxysql_conn, "USE test");
 	MYSQL_QUERY(proxysql_conn, "CREATE TABLE IF NOT EXISTS dummy_log_table (id INT PRIMARY KEY AUTO_INCREMENT, data LONGTEXT)");
-	// Generate enough binlog data so that throttled reads at target_time=20s
-	// actually take longer than the 8s grace close period. Each INSERT creates
-	// a ~50KB binlog event; we need many events so the per-event sleep adds up.
-	for (int i = 0; i < 50; i++) {
+	// Generate enough binlog data that the client's kernel recv buffer can
+	// hold only a small fraction of it. For target_time > 8s, grace close
+	// must fire before the full binlog (including the empty-event EOF marker)
+	// has been delivered to the client's socket — otherwise the client sees
+	// EOF anyway and the "expected FALSE" assertions flake. With autotuned
+	// recv buffers that can grow to several MB on some kernels/runners, a
+	// small binlog lets the EOF marker slip through during the 8s grace
+	// window. 1000 x 50 KB = ~50 MB gives a comfortable multiple of any
+	// realistic recv buffer.
+	for (int i = 0; i < 1000; i++) {
 		MYSQL_QUERY(proxysql_conn, "INSERT INTO dummy_log_table (data) VALUES (REPEAT('a', 1024*50))");
 	}
 	int rc = mysql_query(proxysql_conn, "FLUSH LOGS");