diff --git a/cmsg.cpp b/cmsg.cpp
index 1fa873c..95db303 100644
--- a/cmsg.cpp
+++ b/cmsg.cpp
@@ -31,9 +31,10 @@
 
 ssize_t SendFileDescriptorVector(borrowed_fd sockfd, const void* data, size_t len,
                                  const std::vector<int>& fds) {
+  static const size_t page_size = sysconf(_SC_PAGE_SIZE);
   size_t cmsg_space = CMSG_SPACE(sizeof(int) * fds.size());
   size_t cmsg_len = CMSG_LEN(sizeof(int) * fds.size());
-  if (cmsg_space >= PAGE_SIZE) {
+  if (cmsg_space >= page_size) {
     errno = ENOMEM;
     return -1;
   }
@@ -74,8 +75,9 @@
                                     std::vector<unique_fd>* fds) {
   fds->clear();
 
+  static const size_t page_size = sysconf(_SC_PAGE_SIZE);
   size_t cmsg_space = CMSG_SPACE(sizeof(int) * max_fds);
-  if (cmsg_space >= PAGE_SIZE) {
+  if (cmsg_space >= page_size) {
     errno = ENOMEM;
     return -1;
   }