diff --git a/dep/fmt/CMakeLists.txt b/dep/fmt/CMakeLists.txt
index 6de5ac9260..c7c55ea750 100644
--- a/dep/fmt/CMakeLists.txt
+++ b/dep/fmt/CMakeLists.txt
@@ -10,6 +10,8 @@
 
 set(strtod_l_headers stdlib.h)
 
+include(CheckSymbolExists)
+
 if (APPLE)
   set(strtod_l_headers ${strtod_l_headers} xlocale.h)
 endif ()