diff --git a/src/util.cpp b/src/util.cpp
index b0c80f6dfc4..d143306aecf 100644
--- a/src/util.cpp
+++ b/src/util.cpp
@@ -25,6 +25,7 @@ namespace boost {
 #include <boost/filesystem.hpp>
 #include <boost/filesystem/fstream.hpp>
 #include <boost/foreach.hpp>
+#include <boost/thread.hpp>
 #include <openssl/crypto.h>
 #include <openssl/rand.h>
 #include <stdarg.h>
@@ -209,6 +210,8 @@ inline int OutputDebugStringF(const char* pszFormat, ...)
         if (fileout)
         {
             static bool fStartedNewLine = true;
+            static boost::mutex mutexDebugLog;
+            boost::mutex::scoped_lock scoped_lock(mutexDebugLog);
 
             // Debug print useful for profiling
             if (fLogTimestamps && fStartedNewLine)