diff --git a/broker/src/main/kotlin/dev/usbharu/owl/broker/service/DefaultPropertySerializerFactory.kt b/broker/src/main/kotlin/dev/usbharu/owl/broker/service/DefaultPropertySerializerFactory.kt
index 3e34c65..d35c6e0 100644
--- a/broker/src/main/kotlin/dev/usbharu/owl/broker/service/DefaultPropertySerializerFactory.kt
+++ b/broker/src/main/kotlin/dev/usbharu/owl/broker/service/DefaultPropertySerializerFactory.kt
@@ -1,3 +1,19 @@
+/*
+ * Copyright (C) 2024 usbharu
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
 package dev.usbharu.owl.broker.service
 
 import dev.usbharu.owl.common.property.*
diff --git a/common/src/main/kotlin/dev/usbharu/owl/common/retry/ExponentialRetryPolicy.kt b/common/src/main/kotlin/dev/usbharu/owl/common/retry/ExponentialRetryPolicy.kt
index 60180dd..8745fc1 100644
--- a/common/src/main/kotlin/dev/usbharu/owl/common/retry/ExponentialRetryPolicy.kt
+++ b/common/src/main/kotlin/dev/usbharu/owl/common/retry/ExponentialRetryPolicy.kt
@@ -6,6 +6,6 @@ import kotlin.math.roundToLong
 
 class ExponentialRetryPolicy(private val firstRetrySeconds: Int = 30) : RetryPolicy {
     override fun nextRetry(now: Instant, attempt: Int): Instant =
-        now.plusSeconds(firstRetrySeconds.toDouble().pow(attempt + 1.0).roundToLong())
+        now.plusSeconds(firstRetrySeconds.times((2.0).pow(attempt).roundToLong()))
 
 }
\ No newline at end of file
diff --git a/common/src/test/kotlin/dev/usbharu/owl/common/retry/ExponentialRetryPolicyTest.kt b/common/src/test/kotlin/dev/usbharu/owl/common/retry/ExponentialRetryPolicyTest.kt
new file mode 100644
index 0000000..53ea7a1
--- /dev/null
+++ b/common/src/test/kotlin/dev/usbharu/owl/common/retry/ExponentialRetryPolicyTest.kt
@@ -0,0 +1,36 @@
+/*
+ * Copyright (C) 2024 usbharu
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package dev.usbharu.owl.common.retry
+
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Test
+import java.time.Instant
+
+class ExponentialRetryPolicyTest {
+    @Test
+    fun exponential0() {
+        val nextRetry = ExponentialRetryPolicy().nextRetry(Instant.ofEpochSecond(300), 0)
+
+        assertEquals(Instant.ofEpochSecond(330), nextRetry)
+    }
+
+    @Test
+    fun exponential1() {
+        val nextRetry = ExponentialRetryPolicy().nextRetry(Instant.ofEpochSecond(300), 1)
+        assertEquals(Instant.ofEpochSecond(360), nextRetry)
+    }
+}
\ No newline at end of file