diff --git a/CMakeModules/UseCompat.cmake b/CMakeModules/UseCompat.cmake
index ac330e5..753b10d 100644
--- a/CMakeModules/UseCompat.cmake
+++ b/CMakeModules/UseCompat.cmake
@@ -54,6 +54,7 @@
     check_symbol_exists(realpath "stdlib.h" HAVE_REALPATH)
     check_symbol_exists(localtime_r "time.h" HAVE_LOCALTIME_R)
     check_symbol_exists(strptime "time.h" HAVE_STRPTIME)
+    check_symbol_exists(mmap "sys/mman.h" HAVE_MMAP)
 
     unset(CMAKE_REQUIRED_DEFINITIONS)
     unset(CMAKE_REQUIRED_LIBRARIES)