diff --git a/shiroha-server/src/main/java/io/nanachiyo0721/shiroha/data/BufferedLinearRegionFile.java b/shiroha-server/src/main/java/io/nanachiyo0721/shiroha/data/BufferedLinearRegionFile.java
index 485c782..505ee59 100644
--- a/shiroha-server/src/main/java/io/nanachiyo0721/shiroha/data/BufferedLinearRegionFile.java
+++ b/shiroha-server/src/main/java/io/nanachiyo0721/shiroha/data/BufferedLinearRegionFile.java
@@ -269,13 +269,13 @@ public class BufferedLinearRegionFile implements io.nanachiyo0721.shiroha.data.R
 
     public void syncIfNeeded() throws IOException {
         try {
-            this.syncToMasterFile();
+            this.syncToMasterFile(false, false);
         } finally {
             BEING_SYNCED_HANDLE.setVolatile(this, false); // mark as not being synced
         }
     }
 
-    private void syncToMasterFile() throws IOException {
+    private void syncToMasterFile(boolean forceSync, boolean forceCompact) throws IOException {
         // serialized against close: the swap channel cannot go away under a running sync
         synchronized (this.syncLock) {
             // skip if closed already
@@ -285,12 +285,12 @@ public class BufferedLinearRegionFile implements io.nanachiyo0721.shiroha.data.R
 
             // fast skip when there is nothing to sync; writers flip the flag back
             // via markAsToSync() which triggers the next round
-            if (!SYNCED_HANDLE.compareAndSet(this, false, true)) {
+            if (!SYNCED_HANDLE.compareAndSet(this, false, true) && !forceSync) {
                 return;
             }
 
             try {
-                this.masterFileParser.sync(this.masterFilePath);
+                this.masterFileParser.sync(this.masterFilePath, forceCompact);
             } catch (Throwable e) {
                 // set back
                 SYNCED_HANDLE.setVolatile(this, false);
@@ -403,7 +403,7 @@ public class BufferedLinearRegionFile implements io.nanachiyo0721.shiroha.data.R
         }
 
         if (initiallySyncRequired) {
-            this.syncToMasterFile();
+            this.syncToMasterFile(false, false);
         }
     }
 
@@ -427,7 +427,7 @@ public class BufferedLinearRegionFile implements io.nanachiyo0721.shiroha.data.R
             // concurrent flusher sync is still running when we tear down below.
             // if this throws we deliberately stay open: the flusher can retry the sync
             // later, and the not-yet-synced swap data is not dropped on the floor
-            this.syncToMasterFile();
+            this.syncToMasterFile(true, true);
 
             IOException failure = null;
 
@@ -974,13 +974,13 @@ public class BufferedLinearRegionFile implements io.nanachiyo0721.shiroha.data.R
         }
 
         // must be called under syncLock (see syncToMasterFile)
-        public void sync(@NotNull Path mainFile) throws IOException {
+        public void sync(@NotNull Path mainFile, boolean forceCompact) throws IOException {
             this.masterFileLock.writeLock().lock();
             try {
                 // full rewrite on the first sync after open, and afterwards whenever the
                 // appended garbage passed the auto-compact threshold: writes a tmp file,
                 // then atomically replaces the master file with it
-                if (this.appendChannel == null || this.shouldCompactMasterFile()) {
+                if (this.appendChannel == null || this.shouldCompactMasterFile() || forceCompact) {
                     this.rewriteFully(mainFile);
                 } else {
                     // WAL-style otherwise: only append the dirty buckets
@@ -1589,7 +1589,7 @@ public class BufferedLinearRegionFile implements io.nanachiyo0721.shiroha.data.R
             // old parsed, remove the original file, and we will recreate it as we sync
             if (oldParsed) {
                 // immediately do sync operation
-                BufferedLinearRegionFile.this.syncToMasterFile();
+                BufferedLinearRegionFile.this.syncToMasterFile(true, true);
                 return;
             }