diff --git a/CMakeLists.txt b/CMakeLists.txt
index a40f737ad03b..1d390aa54348 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -242,7 +242,7 @@ if(MBEDTLS_FATAL_WARNINGS)
     endif(CMAKE_COMPILER_IS_CLANG OR CMAKE_COMPILER_IS_GNU)
 
     if (CMAKE_COMPILER_IS_IAR)
-        set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} --warning_are_errors")
+        set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} --warnings_are_errors")
     endif(CMAKE_COMPILER_IS_IAR)
 endif(MBEDTLS_FATAL_WARNINGS)