diff --git a/cmake/Modules/Platform/Emscripten.cmake b/cmake/Modules/Platform/Emscripten.cmake
index 90e58037750be..d960e436c5599 100644
--- a/cmake/Modules/Platform/Emscripten.cmake
+++ b/cmake/Modules/Platform/Emscripten.cmake
@@ -266,7 +266,9 @@ if (EMSCRIPTEN_GENERATE_BITCODE_STATIC_LIBRARIES)
   message(FATAL_ERROR "EMSCRIPTEN_GENERATE_BITCODE_STATIC_LIBRARIES is not compatible with the llvm backend")
 endif()
 
-set(CMAKE_EXECUTABLE_SUFFIX ".js")
+if(NOT DEFINED CMAKE_EXECUTABLE_SUFFIX)
+  set(CMAKE_EXECUTABLE_SUFFIX ".js")
+endif()
 
 set(CMAKE_C_USE_RESPONSE_FILE_FOR_LIBRARIES 1)
 set(CMAKE_CXX_USE_RESPONSE_FILE_FOR_LIBRARIES 1)