diff --git a/util/linux/socket.cc b/util/linux/socket.cc
index f2ad9bd0..868cee4a 100644
--- a/util/linux/socket.cc
+++ b/util/linux/socket.cc
@@ -23,6 +23,8 @@
 
 namespace crashpad {
 
+constexpr size_t UnixCredentialSocket::kMaxSendRecvMsgFDs;
+
 // static
 bool UnixCredentialSocket::CreateCredentialSocketpair(ScopedFileHandle* sock1,
                                                       ScopedFileHandle* sock2) {
@@ -49,8 +51,6 @@ bool UnixCredentialSocket::CreateCredentialSocketpair(ScopedFileHandle* sock1,
   return true;
 }
 
-constexpr size_t UnixCredentialSocket::kMaxSendRecvMsgFDs = 4;
-
 // static
 int UnixCredentialSocket::SendMsg(int fd,
                                   const void* buf,
diff --git a/util/linux/socket.h b/util/linux/socket.h
index 85860f7b..d762592b 100644
--- a/util/linux/socket.h
+++ b/util/linux/socket.h
@@ -40,7 +40,7 @@ class UnixCredentialSocket {
 
   //! \brief The maximum number of file descriptors that may be sent/received
   //!     with `SendMsg()` or `RecvMsg()`.
-  static const size_t kMaxSendRecvMsgFDs;
+  static constexpr size_t kMaxSendRecvMsgFDs = 4;
 
   //! \brief Wraps `sendmsg()` to send a message with file descriptors.
   //!