diff --git a/test/src/e2e.long/sync2.test.ts b/test/src/e2e.long/sync2.test.ts
index f63f821e25..93e8ae0834 100644
--- a/test/src/e2e.long/sync2.test.ts
+++ b/test/src/e2e.long/sync2.test.ts
@@ -25,8 +25,10 @@ describe("sync 2 nodes", function() {
 
     describe("2 nodes", function() {
         beforeEach(async function() {
-            nodeA = new CodeChain();
-            nodeB = new CodeChain();
+            // To generate a block this test sends a tx to a node.
+            // If the tx is propagated before generating a block, tests in this file would fail.
+            nodeA = new CodeChain({ argv: ["--no-tx-relay"] });
+            nodeB = new CodeChain({ argv: ["--no-tx-relay"] });
 
             await Promise.all([nodeA.start(), nodeB.start()]);
         });
diff --git a/test/src/e2e.long/sync3.test.ts b/test/src/e2e.long/sync3.test.ts
index ab724ad702..12ac312a89 100644
--- a/test/src/e2e.long/sync3.test.ts
+++ b/test/src/e2e.long/sync3.test.ts
@@ -28,7 +28,9 @@ describe("sync 3 nodes", function() {
         nodes = [];
         for (let i = 0; i < NUM_NODES; i++) {
             const node = new CodeChain({
-                argv: ["--no-discovery"]
+                // To generate a block this test sends a tx to a node.
+                // If the tx is propagated before generating a block, tests in this file would fail.
+                argv: ["--no-discovery", "--no-tx-relay"]
             });
             nodes.push(node);
         }
diff --git a/test/src/e2e.long/sync5.test.ts b/test/src/e2e.long/sync5.test.ts
index 32f02aa903..b905925372 100644
--- a/test/src/e2e.long/sync5.test.ts
+++ b/test/src/e2e.long/sync5.test.ts
@@ -27,8 +27,10 @@ describe("sync 5 nodes", function() {
 
         nodes = [];
         for (let i = 0; i < NUM_NODES; i++) {
+            // To generate a block this test sends a tx to a node.
+            // If the tx is propagated before generating a block, tests in this file would fail.
             const node = new CodeChain({
-                argv: ["--no-discovery"]
+                argv: ["--no-discovery", "--no-tx-relay"]
             });
             nodes.push(node);
         }