diff --git a/Library/Homebrew/extend/os/mac/hardware.rb b/Library/Homebrew/extend/os/mac/hardware.rb
index fb5d8bd58e..0649eddaa9 100644
--- a/Library/Homebrew/extend/os/mac/hardware.rb
+++ b/Library/Homebrew/extend/os/mac/hardware.rb
@@ -7,6 +7,8 @@ module Hardware
   def self.oldest_cpu(version = MacOS.version)
     if CPU.arch == :arm64
       :arm_vortex_tempest
+    elsif version >= :big_sur
+      :ivybridge
     elsif version >= :mojave
       :nehalem
     else
diff --git a/Library/Homebrew/hardware.rb b/Library/Homebrew/hardware.rb
index f03078f877..1bdfe99a78 100644
--- a/Library/Homebrew/hardware.rb
+++ b/Library/Homebrew/hardware.rb
@@ -26,8 +26,9 @@ module Hardware
       def optimization_flags
         @optimization_flags ||= {
           native:             arch_flag("native"),
-          nehalem:            "-march=nehalem",
+          ivybridge:          "-march=ivybridge",
           sandybridge:        "-march=sandybridge",
+          nehalem:            "-march=nehalem",
           core2:              "-march=core2",
           core:               "-march=prescott",
           arm_vortex_tempest: "",