diff --git a/BufferedTextOutput.cpp b/BufferedTextOutput.cpp
index 1339a67..a2443c0 100644
--- a/BufferedTextOutput.cpp
+++ b/BufferedTextOutput.cpp
@@ -34,7 +34,7 @@
 
 struct BufferedTextOutput::BufferState : public RefBase
 {
-    BufferState(int32_t _seq)
+    explicit BufferState(int32_t _seq)
         : seq(_seq)
         , buffer(NULL)
         , bufferPos(0)