diff --git a/src/config/CMakeLists.txt b/src/config/CMakeLists.txt
--- a/src/config/CMakeLists.txt
+++ b/src/config/CMakeLists.txt
@@ -134,6 +134,8 @@
 check_symbol_exists(getifaddrs "sys/types.h;ifaddrs.h" HAVE_DECL_GETIFADDRS)
 check_symbol_exists(freeifaddrs "sys/types.h;ifaddrs.h" HAVE_DECL_FREEIFADDRS)
 
+check_symbol_exists(fdatasync "unistd.h" HAVE_FDATASYNC)
+
 check_cxx_source_compiles("
 	#include <unistd.h>  /* for syscall */
 	#include <sys/syscall.h>  /* for SYS_getrandom */
diff --git a/src/util/system.cpp b/src/util/system.cpp
--- a/src/util/system.cpp
+++ b/src/util/system.cpp
@@ -3,6 +3,10 @@
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
+#if defined(HAVE_CONFIG_H)
+#include <config/bitcoin-config.h> // For HAVE_FDATASYNC
+#endif
+
 #include <util/system.h>
 
 #include <chainparamsbase.h>
@@ -1141,7 +1145,7 @@
         return false;
     }
 #else
-#if defined(HAVE_FDATASYNC)
+#if HAVE_FDATASYNC
     // Ignore EINVAL for filesystems that don't support sync
     if (fdatasync(fileno(file)) != 0 && errno != EINVAL) {
         LogPrintf("%s: fdatasync failed: %d\n", __func__, errno);