diff --git a/app/src/main/java/io/legado/app/service/CheckSourceService.kt b/app/src/main/java/io/legado/app/service/CheckSourceService.kt
index 437bc41c4..19c839aff 100644
--- a/app/src/main/java/io/legado/app/service/CheckSourceService.kt
+++ b/app/src/main/java/io/legado/app/service/CheckSourceService.kt
@@ -64,7 +64,9 @@ class CheckSourceService : BaseService() {
 
 
     private fun check() {
-        processIndex++
+        synchronized(this) {
+            processIndex++
+        }
         if (processIndex < allIds.size) {
             val sourceUrl = allIds[processIndex]
 
@@ -81,8 +83,10 @@ class CheckSourceService : BaseService() {
                             checkedIds.size,
                             getString(R.string.progress_show, checkedIds.size, allIds.size)
                         )
-                        if (processIndex >= allIds.size + threadCount - 1) {
-                            stopSelf()
+                        synchronized(this) {
+                            if (processIndex >= allIds.size + threadCount - 1) {
+                                stopSelf()
+                            }
                         }
                     }
             }