diff --git a/CMakeLists.txt b/CMakeLists.txt
index 287a889ed35be6114e90dcf7ba63724daca5de1d..125269efb38c571babf5e2d417e1e6bd2b5232b6 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -74,7 +74,7 @@ check_include_file(cpuid.h HAVE_CPUID_H)
 check_include_file(sys/prctl.h HAVE_PRCTL_H)
 
 check_symbol_exists(O_DSYNC fcntl.h HAVE_O_DSYNC)
-check_function_exists(fdatasync HAVE_FDATASYNC)
+check_symbol_exists(fdatasync unistd.h HAVE_FDATASYNC)
 check_function_exists(memmem HAVE_MEMMEM)
 check_function_exists(memrchr HAVE_MEMRCHR)