diff --git a/server/SockDiag.cpp b/server/SockDiag.cpp
index b9f69cd..cd96a26 100644
--- a/server/SockDiag.cpp
+++ b/server/SockDiag.cpp
@@ -176,7 +176,7 @@
     return checkError(mSock);
 }
 
-int SockDiag::readDiagMsg(uint8_t proto, SockDiag::DumpCallback callback) {
+int SockDiag::readDiagMsg(uint8_t proto, const SockDiag::DumpCallback& callback) {
     char buf[kBufferSize];
 
     ssize_t bytesread;
diff --git a/server/SockDiag.h b/server/SockDiag.h
index 56acbdb..ccd54bf 100644
--- a/server/SockDiag.h
+++ b/server/SockDiag.h
@@ -23,7 +23,7 @@
     virtual ~SockDiag() { closeSocks(); }
 
     int sendDumpRequest(uint8_t proto, uint8_t family, const char *addrstr);
-    int readDiagMsg(uint8_t proto, DumpCallback callback);
+    int readDiagMsg(uint8_t proto, const DumpCallback& callback);
     int sockDestroy(uint8_t proto, const inet_diag_msg *);
     int destroySockets(const char *addrstr);