diff --git a/Library/Homebrew/brew.sh b/Library/Homebrew/brew.sh
index ebea36c38c..942a8ae422 100644
--- a/Library/Homebrew/brew.sh
+++ b/Library/Homebrew/brew.sh
@@ -167,6 +167,7 @@ export HOMEBREW_PROCESSOR
 export HOMEBREW_PRODUCT
 export HOMEBREW_OS_VERSION
 export HOMEBREW_MACOS_VERSION
+export HOMEBREW_MACOS_VERSION_NUMERIC
 export HOMEBREW_USER_AGENT
 export HOMEBREW_USER_AGENT_CURL
 
diff --git a/Library/Homebrew/shims/scm/git b/Library/Homebrew/shims/scm/git
index 7306268fda..0930c0adc3 100755
--- a/Library/Homebrew/shims/scm/git
+++ b/Library/Homebrew/shims/scm/git
@@ -122,12 +122,7 @@ then
   xcode_path="$(/usr/bin/xcode-select -print-path 2>/dev/null)"
   if [[ -z "$xcode_path" ]]
   then
-    if [[ -z "$HOMEBREW_MACOS_VERSION" ]]
-    then
-      HOMEBREW_MACOS_VERSION="$(/usr/bin/sw_vers -productVersion)"
-    fi
-    printf -v macos_version_numeric "%02d%02d%02d" ${HOMEBREW_MACOS_VERSION//./ }
-    if [[ "$macos_version_numeric" -ge "100900" ]]
+    if [[ "$HOMEBREW_MACOS_VERSION_NUMERIC" -ge "100900" ]]
     then
       popup_stub=1
     fi
diff --git a/Library/Homebrew/shims/super/cc b/Library/Homebrew/shims/super/cc
index 0ea2f6e4e9..bbab4c448c 100755
--- a/Library/Homebrew/shims/super/cc
+++ b/Library/Homebrew/shims/super/cc
@@ -18,7 +18,7 @@ def mac?
 end
 
 def high_sierra_or_later?
-  mac? && RUBY_PLATFORM[/darwin\d+/][/\d+/].to_i >= 17
+  mac? && ENV["HOMEBREW_MACOS_VERSION_NUMERIC"].to_s.to_i >= 101300
 end
 
 def linux?