diff --git a/application/src/main/java/run/halo/app/core/attachment/impl/ThumbnailServiceImpl.java b/application/src/main/java/run/halo/app/core/attachment/impl/ThumbnailServiceImpl.java
index b8c1508fb..d77a94ba9 100644
--- a/application/src/main/java/run/halo/app/core/attachment/impl/ThumbnailServiceImpl.java
+++ b/application/src/main/java/run/halo/app/core/attachment/impl/ThumbnailServiceImpl.java
@@ -50,8 +50,9 @@ public class ThumbnailServiceImpl implements ThumbnailService {
         // restriction
         return ongoingTasks.computeIfAbsent(cacheKey, k -> doGenerate(imageUri, size)
             // In the case of concurrency, doGenerate must return the same instance
+            .doFinally(signalType -> ongoingTasks.remove(cacheKey))
             .cache()
-            .doFinally(signalType -> ongoingTasks.remove(cacheKey)));
+        );
     }
 
     record CacheKey(URI imageUri, ThumbnailSize size) {
diff --git a/application/src/test/java/run/halo/app/core/attachment/impl/ThumbnailServiceImplTest.java b/application/src/test/java/run/halo/app/core/attachment/impl/ThumbnailServiceImplTest.java
index 6821b6be1..c1c1433cc 100644
--- a/application/src/test/java/run/halo/app/core/attachment/impl/ThumbnailServiceImplTest.java
+++ b/application/src/test/java/run/halo/app/core/attachment/impl/ThumbnailServiceImplTest.java
@@ -192,7 +192,7 @@ class ThumbnailServiceImplTest {
             var createdUri = URI.create("/test-thumb.jpg");
             doReturn(Mono.just(createdUri)).when(spyThumbnailService).create(any(), any());
 
-            int threadCount = 10;
+            int threadCount = 100;
             ExecutorService executor = Executors.newFixedThreadPool(threadCount);
             var latch = new CountDownLatch(threadCount);