diff --git a/cmake/modules/ErrorFlags.cmake b/cmake/modules/ErrorFlags.cmake
index bc0d84bb1..836a4da26 100644
--- a/cmake/modules/ErrorFlags.cmake
+++ b/cmake/modules/ErrorFlags.cmake
@@ -44,9 +44,6 @@ if(CMAKE_CXX_COMPILER_ID MATCHES "GNU|Clang")
 			"-Werror" # Treat warnings as errors
 		)
 	endif()
-
-	set(SILENCE_DEPRECATION_DEFS "")
-	set(THIRD_PARTY_SILENCE_DEPRECATION_DEFS "")
 elseif(MSVC)
 	set(COMPILE_ERROR_FLAGS
 		"/W2" # Enable some warnings by default
@@ -69,11 +66,9 @@ elseif(MSVC)
 		)
 	endif()
 
-	set(SILENCE_DEPRECATION_DEFS "_SILENCE_CXX20_OLD_SHARED_PTR_ATOMIC_SUPPORT_DEPRECATION_WARNING")
-	set(THIRD_PARTY_SILENCE_DEPRECATION_DEFS "")
+	add_compile_definitions("_SILENCE_CXX20_OLD_SHARED_PTR_ATOMIC_SUPPORT_DEPRECATION_WARNING")
 endif()
 
 # Add the flags to the whole directory tree. We use the third-party flags for
 # targets whose SYSTEM property is true, and the normal flags otherwise.
 add_compile_options("$<IF:$<BOOL:$<TARGET_PROPERTY:SYSTEM>>,${THIRD_PARTY_COMPILE_ERROR_FLAGS},${COMPILE_ERROR_FLAGS}>")
-add_compile_definitions("$<IF:$<BOOL:$<TARGET_PROPERTY:SYSTEM>>,${THIRD_PARTY_SILENCE_DEPRECATION_DEFS},${SILENCE_DEPRECATION_DEFS}>")