diff --git a/CMakeLists.txt b/CMakeLists.txt
index 36d6cbd..57a0c74 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -30,8 +30,13 @@ check_library_exists(crc32c crc32c_value "" HAVE_CRC32C)
 check_library_exists(snappy snappy_compress "" HAVE_SNAPPY)
 check_library_exists(tcmalloc malloc "" HAVE_TCMALLOC)
 
-include(CheckSymbolExists)
-check_symbol_exists(fdatasync "unistd.h" HAVE_FDATASYNC)
+include(CheckCXXSymbolExists)
+# Using check_cxx_symbol_exists() instead of check_c_symbol_exists() because
+# we're including the header from C++, and feature detection should use the same
+# compiler language that the project will use later. Principles aside, some
+# versions of do not expose fdatasync() in <unistd.h> in standard C mode
+# (-std=c11), but do expose the function in standard C++ mode (-std=c++11).
+check_cxx_symbol_exists(fdatasync "unistd.h" HAVE_FDATASYNC)
 
 include(CheckCXXSourceCompiles)
 
diff --git a/port/port_config.h.in b/port/port_config.h.in
index 1934055..645c78c 100644
--- a/port/port_config.h.in
+++ b/port/port_config.h.in
@@ -6,9 +6,9 @@
 #define STORAGE_LEVELDB_PORT_PORT_CONFIG_H_
 
 // Define to 1 if you have a definition for fdatasync() in <unistd.h>.
-#if !defined(HAVE_FUNC_FDATASYNC)
-#cmakedefine01 HAVE_FUNC_FDATASYNC
-#endif  // !defined(HAVE_FUNC_FDATASYNC)
+#if !defined(HAVE_FDATASYNC)
+#cmakedefine01 HAVE_FDATASYNC
+#endif  // !defined(HAVE_FDATASYNC)
 
 // Define to 1 if you have Google CRC32C.
 #if !defined(HAVE_CRC32C)