diff --git a/src/libsync/syncengine.cpp b/src/libsync/syncengine.cpp
index c4197c79bb..0f9907ca49 100644
--- a/src/libsync/syncengine.cpp
+++ b/src/libsync/syncengine.cpp
@@ -851,6 +851,12 @@ void SyncEngine::startSync()
 
     _csync_ctx->new_files_are_placeholders = _syncOptions._newFilesArePlaceholders;
     _csync_ctx->placeholder_suffix = _syncOptions._placeholderSuffix.toUtf8();
+    if (_csync_ctx->new_files_are_placeholders && _csync_ctx->placeholder_suffix.isEmpty()) {
+        csyncError(tr("Using placeholder files, but placeholder suffix is not set"));
+        finalize(false);
+        return;
+    }
+
     bool ok;
     auto selectiveSyncBlackList = _journal->getSelectiveSyncList(SyncJournalDb::SelectiveSyncBlackList, &ok);
     if (ok) {
diff --git a/src/libsync/syncoptions.h b/src/libsync/syncoptions.h
index 2e302bda94..ea48cd83e1 100644
--- a/src/libsync/syncoptions.h
+++ b/src/libsync/syncoptions.h
@@ -38,7 +38,7 @@ struct SyncOptions
 
     /** Create a placeholder for new files instead of downloading */
     bool _newFilesArePlaceholders = false;
-    QString _placeholderSuffix;
+    QString _placeholderSuffix = ".owncloud";
 
     /** The initial un-adjusted chunk size in bytes for chunked uploads, both
      * for old and new chunking algorithm, which classifies the item to be chunked