diff --git a/CMLibCompilerFlags.cmake b/CMLibCompilerFlags.cmake
index 9023444..d500308 100644
--- a/CMLibCompilerFlags.cmake
+++ b/CMLibCompilerFlags.cmake
@@ -18,18 +18,20 @@ macro(CHECK_ENABLE_CXX_FLAG flag)
 endmacro()
 
 macro(CHECK_ENABLE_DEBUG_CXX_FLAG flag)
-  set(CMAKE_REQUIRED_QUIET TRUE)
-  check_cxx_compiler_flag("${flag}" CHECK_CXX_FLAG_DEBUG)
-  unset(CMAKE_REQUIRED_QUIET)
+  if(CMAKE_BUILD_TYPE STREQUAL "Debug")
+    set(CMAKE_REQUIRED_QUIET TRUE)
+    check_cxx_compiler_flag("${flag}" CHECK_CXX_FLAG_DEBUG)
+    unset(CMAKE_REQUIRED_QUIET)
 
-  if(CHECK_CXX_FLAG_DEBUG)
-    message(STATUS "'${flag}': debug flag is supported.")
-    string(CONCAT _CMLIB_DETECTED_CXX_FLAGS_DEBUG "${_CMLIB_DETECTED_CXX_FLAGS_DEBUG} ${flag}")
-  else()
-    message(STATUS "'${flag}': debug flag is NOT supported.")
+    if(CHECK_CXX_FLAG_DEBUG)
+      message(STATUS "'${flag}': debug flag is supported.")
+      string(CONCAT _CMLIB_DETECTED_CXX_FLAGS_DEBUG "${_CMLIB_DETECTED_CXX_FLAGS_DEBUG} ${flag}")
+    else()
+      message(STATUS "'${flag}': debug flag is NOT supported.")
+    endif()
+    # NOTE: check_cxx_compiler stores variables in the cache.
+    unset(CHECK_CXX_FLAG_DEBUG CACHE)
   endif()
-  # NOTE: check_cxx_compiler stores variables in the cache.
-  unset(CHECK_CXX_FLAG_DEBUG CACHE)
 endmacro()
 
 function(cmlib_set_cxx_standard version)