diff --git a/CMakeLists.txt b/CMakeLists.txt
index 17ee3fc2956c40d352516269cf2382f59adb493d..c01ec57caa5626afa68a6381e50d8c4c387d0cdd 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -186,7 +186,7 @@ target_link_libraries(opus PRIVATE ${OPUS_REQUIRED_LIBRARIES})
 target_compile_definitions(opus PRIVATE OPUS_BUILD ENABLE_HARDENING)
 
 if(NOT MSVC)
-  target_compile_definitions(opus PRIVATE FORTIFY_SOURCE=2)
+  target_compile_definitions(opus PRIVATE _FORTIFY_SOURCE=2)
 endif()
 
 # It is strongly recommended to uncomment one of these VAR_ARRAYS: Use C99