diff --git a/Modules/Compiler/Intel-C.cmake b/Modules/Compiler/Intel-C.cmake
index eb9602a..edca154 100644
--- a/Modules/Compiler/Intel-C.cmake
+++ b/Modules/Compiler/Intel-C.cmake
@@ -16,14 +16,14 @@ endif()
 
 if (NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 15.0.0)
   set(CMAKE_C11_STANDARD_COMPILE_OPTION "${_std}=c11")
-  set(CMAKE_C11_EXTENSION_COMPILE_OPTION "${_std}=c11")
+  set(CMAKE_C11_EXTENSION_COMPILE_OPTION "${_std}=gnu11")
 endif()
 
-if (NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 12.1)
+if (NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 12.0)
   set(CMAKE_C90_STANDARD_COMPILE_OPTION "${_std}=c89")
-  set(CMAKE_C90_EXTENSION_COMPILE_OPTION "${_std}=c89")
+  set(CMAKE_C90_EXTENSION_COMPILE_OPTION "${_std}=gnu89")
   set(CMAKE_C99_STANDARD_COMPILE_OPTION "${_std}=c99")
-  set(CMAKE_C99_EXTENSION_COMPILE_OPTION "${_std}=c99")
+  set(CMAKE_C99_EXTENSION_COMPILE_OPTION "${_std}=gnu99")
 endif()
 
 if(NOT CMAKE_C_COMPILER_VERSION VERSION_LESS 12.1)