diff --git a/nc_optimisation.cmake b/nc_optimisation.cmake
index aecd8ba..a1dad10 100644
--- a/nc_optimisation.cmake
+++ b/nc_optimisation.cmake
@@ -214,7 +214,10 @@ if (CMAKE_BUILD_TYPE MATCHES Debug)
     endif()
 else ()
     append_compile_flag(-O2)
-    append_compile_flag(-fno-rtti)
+    # Some dependencies (eg, fmtlib) unconditionally use `dynamic_cast` so need RTTI enabled.
+    if (NOT WIN32)
+        append_compile_flag(-fno-rtti)
+    endif ()
     add_definitions(-DNO_RTTI)
     add_definitions(-DNDEBUG)
 endif ()