diff --git a/CMakeLists.txt b/CMakeLists.txt
index 18c09b2..76530f2 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -89,7 +89,7 @@ if (${IS_GNU} OR ${IS_CLANG})
     set(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} -ffunction-sections -fdata-sections -fmerge-all-constants -ftree-vectorize -fno-math-errno")
     include(CheckCXXCompilerFlag)
     check_cxx_compiler_flag("-Oz" Z_OPTIMIZATION_SUPPORTED)
-    if (Z_OPTIMIZATION_SUPPORTED)
+    if (Z_OPTIMIZATION_SUPPORTED OR EMSCRIPTEN)
         set(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} -Oz")
     endif()
     set(CF_PROTECTION "-fcf-protection")