diff --git a/service/src/main/kotlin/com/sangdol/roomescape/payment/business/PaymentService.kt b/service/src/main/kotlin/com/sangdol/roomescape/payment/business/PaymentService.kt
index dc77b7bb..8336919c 100644
--- a/service/src/main/kotlin/com/sangdol/roomescape/payment/business/PaymentService.kt
+++ b/service/src/main/kotlin/com/sangdol/roomescape/payment/business/PaymentService.kt
@@ -41,6 +41,9 @@ class PaymentService(
             val detail: PaymentDetailEntity = paymentWriter.createDetail(clientConfirmResponse, payment.id)
 
             PaymentCreateResponse(paymentId = payment.id, detailId = detail.id)
+        } ?: run {
+            log.warn { "[PaymentService.confirm] 결제 확정 중 예상치 못한 null 반환" }
+            throw PaymentException(PaymentErrorCode.PAYMENT_UNEXPECTED_ERROR)
         }
     }
 
diff --git a/service/src/test/kotlin/com/sangdol/data/DefaultDataInitializer.kt b/service/src/test/kotlin/com/sangdol/data/DefaultDataInitializer.kt
index 43d88804..04f7ab1c 100644
--- a/service/src/test/kotlin/com/sangdol/data/DefaultDataInitializer.kt
+++ b/service/src/test/kotlin/com/sangdol/data/DefaultDataInitializer.kt
@@ -135,7 +135,7 @@ class DefaultDataInitializer : AbstractDataInitializer() {
                             listOf(AdminPermissionLevel.FULL_ACCESS, AdminPermissionLevel.WRITABLE)
                         )
                         .resultList
-                }.map { it.toString() }
+                }!!.map { it.toString() }
 
                 val sqlFile = storeDataInitializer.createStoreDataSqlFile(creatableAdminIds)
 
@@ -156,7 +156,7 @@ class DefaultDataInitializer : AbstractDataInitializer() {
                         "SELECT s.id FROM StoreEntity s",
                         Long::class.java
                     ).resultList
-                }.map { it as Long }
+                }!!.map { it as Long }
 
                 transactionExecutionUtil.withNewTransaction(isReadOnly = false) {
                     storeIds.forEach { storeId ->
@@ -209,7 +209,7 @@ class DefaultDataInitializer : AbstractDataInitializer() {
                             listOf(AdminPermissionLevel.FULL_ACCESS, AdminPermissionLevel.WRITABLE)
                         )
                         .resultList
-                }
+                }!!
                 val sql =
                     "INSERT INTO theme (id, name, description, thumbnail_url, is_active, available_minutes, expected_minutes_from, expected_minutes_to, price, difficulty, min_participants, max_participants, created_at, created_by, updated_at, updated_by) VALUES (?," +
                             "?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)"
@@ -270,7 +270,7 @@ class UserDataInitializer : AbstractDataInitializer() {
                         "SELECT r.code FROM RegionEntity r",
                         String::class.java
                     ).resultList
-                }
+                }!!
 
                 val chunkSize = 10_000
                 val chunks = userCount / chunkSize
@@ -299,7 +299,7 @@ class UserDataInitializer : AbstractDataInitializer() {
                         """.trimIndent(),
                             UserEntity::class.java
                         ).resultList
-                    }
+                    }!!
 
                 jdbcTemplate.execute("CREATE INDEX idx_users__phone ON users (phone)")
 
@@ -338,7 +338,7 @@ class UserDataInitializer : AbstractDataInitializer() {
                         "SELECT u.id FROM UserEntity u",
                         Long::class.java
                     ).resultList
-                }
+                }!!
 
                 coroutineScope {
                     userId.chunked(10_000).map { chunk ->
@@ -494,7 +494,7 @@ class ScheduleDataInitializer : AbstractDataInitializer() {
             ).setParameter("type", AdminType.STORE)
                 .setParameter("permissionLevel", AdminPermissionLevel.FULL_ACCESS)
                 .resultList
-        }.map {
+        }!!.map {
             val array = it as List<*>
             Pair(array[0] as Long, array[1] as Long)
         }
@@ -507,7 +507,7 @@ class ScheduleDataInitializer : AbstractDataInitializer() {
                 List::class.java
             )
                 .resultList
-        }.map {
+        }!!.map {
             val array = it as List<*>
             Triple(array[0] as Long, array[1] as Short, array[2] as LocalDateTime)
         }