diff --git a/cmake/config-ix.cmake b/cmake/config-ix.cmake
index 88eaa740175..b380a48637f 100755
--- a/cmake/config-ix.cmake
+++ b/cmake/config-ix.cmake
@@ -94,7 +94,7 @@ endif()
 check_symbol_exists(getpagesize unistd.h HAVE_GETPAGESIZE)
 check_symbol_exists(getrusage sys/resource.h HAVE_GETRUSAGE)
 check_symbol_exists(setrlimit sys/resource.h HAVE_SETRLIMIT)
-check_function_exists(isatty HAVE_ISATTY)
+check_symbol_exists(isatty unistd.h HAVE_ISATTY)
 check_symbol_exists(index strings.h HAVE_INDEX)
 check_symbol_exists(isinf cmath HAVE_ISINF_IN_CMATH)
 check_symbol_exists(isinf math.h HAVE_ISINF_IN_MATH_H)