diff --git a/lib/config/configcompiler.cpp b/lib/config/configcompiler.cpp
index a9f99d485..1021b54d0 100644
--- a/lib/config/configcompiler.cpp
+++ b/lib/config/configcompiler.cpp
@@ -30,6 +30,7 @@
 using namespace icinga;
 
 std::vector<String> ConfigCompiler::m_IncludeSearchDirs;
+boost::mutex ConfigCompiler::m_ZoneDirsMutex;
 std::map<String, std::vector<ZoneFragment> > ConfigCompiler::m_ZoneDirs;
 
 /**
@@ -305,8 +306,8 @@ void ConfigCompiler::AddIncludeSearchDir(const String& dir)
 
 std::vector<ZoneFragment> ConfigCompiler::GetZoneDirs(const String& zone)
 {
-	std::map<String, std::vector<ZoneFragment> >::const_iterator it;
-	it = m_ZoneDirs.find(zone);
+	boost::mutex::scoped_lock lock(m_ZoneDirsMutex);
+	std::map<String, std::vector<ZoneFragment> >::const_iterator it = m_ZoneDirs.find(zone);
 	if (it == m_ZoneDirs.end())
 		return std::vector<ZoneFragment>();
 	else
@@ -318,6 +319,8 @@ void ConfigCompiler::RegisterZoneDir(const String& tag, const String& ppath, con
 	ZoneFragment zf;
 	zf.Tag = tag;
 	zf.Path = ppath;
+
+	boost::mutex::scoped_lock lock(m_ZoneDirsMutex);
 	m_ZoneDirs[zoneName].push_back(zf);
 }
 
diff --git a/lib/config/configcompiler.hpp b/lib/config/configcompiler.hpp
index 3a9a08257..41d981585 100644
--- a/lib/config/configcompiler.hpp
+++ b/lib/config/configcompiler.hpp
@@ -130,6 +130,7 @@ private:
 	void *m_Scanner;
 
 	static std::vector<String> m_IncludeSearchDirs;
+	static boost::mutex m_ZoneDirsMutex;
 	static std::map<String, std::vector<ZoneFragment> > m_ZoneDirs;
 
 	void InitializeScanner(void);