diff --git a/src/net/SocketDescriptor.cxx b/src/net/SocketDescriptor.cxx
index 8b597030..0b172791 100644
--- a/src/net/SocketDescriptor.cxx
+++ b/src/net/SocketDescriptor.cxx
@@ -241,7 +241,7 @@ SocketDescriptor::GetPeerCredentials() const noexcept
 
 #ifdef __linux__
 
-#ifndef SO_PEERCRED
+#ifndef SO_PEERPIDFD
 #define SO_PEERPIDFD 77
 #endif