diff --git a/objectstore/Agent.cpp b/objectstore/Agent.cpp
index 53f955309b6408984b8d0d5f321b06435c8f39e7..5cd34ff046dfd628082cabc158cf09bb02a01c69 100644
--- a/objectstore/Agent.cpp
+++ b/objectstore/Agent.cpp
@@ -9,6 +9,7 @@
 #include <sys/syscall.h>
 #include <ctime>
 #include <cxxabi.h>
+#include <unistd.h>
 
 cta::objectstore::Agent::Agent(Backend & os): 
   ObjectOps<serializers::Agent>(os), m_nextId(0) {}