diff --git a/CMakeLists.txt b/CMakeLists.txt
index e2976bbc..2895f208 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -431,9 +431,18 @@ if(CMAKE_C_COMPILER_ID MATCHES "AppleClang|Clang|GNU|Intel")
   endif()
 endif()
 
+# Compiler and architecture specific flags
 if(CMAKE_C_COMPILER_ID MATCHES "AppleClang|Clang|GNU|Intel" AND NOT CMAKE_SYSTEM_NAME MATCHES "Haiku")
   if(MI_OPT_ARCH)
-    if(MI_ARCH STREQUAL "x64")
+    if(APPLE AND CMAKE_C_COMPILER_ID STREQUAL "AppleClang" AND CMAKE_OSX_ARCHITECTURES)   # to support multi-arch binaries (#999)
+      set(MI_OPT_ARCH_FLAGS "")
+      if("arm64" IN_LIST CMAKE_OSX_ARCHITECTURES)
+        list(APPEND MI_OPT_ARCH_FLAGS "-Xarch_arm64;-march=armv8.1-a")
+      endif()
+      if("x86_64" IN_LIST CMAKE_OSX_ARCHITECTURES)
+        list(APPEND MI_OPT_ARCH_FLAGS "-Xarch_x86_64;-march=haswell;-Xarch_x86_64;-mavx2")
+      endif()
+    elseif(MI_ARCH STREQUAL "x64")
       set(MI_OPT_ARCH_FLAGS "-march=haswell;-mavx2;-mtune=native")    # fast bit scan (since 2013)
     elseif(MI_ARCH STREQUAL "arm64")
       set(MI_OPT_ARCH_FLAGS "-march=armv8.1-a;-mtune=native")         # fast atomics (since 2016)