diff --git a/install.sh b/install.sh
index b63486dd..8a135265 100755
--- a/install.sh
+++ b/install.sh
@@ -12,10 +12,11 @@ set -e
 echo "Installing GitHub Copilot CLI..."
 
 # Detect platform
-case "$(uname -s || echo "")" in
+OS="$(uname -s || echo "")"
+case "$OS" in
   Darwin*) PLATFORM="darwin" ;;
   Linux*) PLATFORM="linux" ;;
-  *)
+  CYGWIN*|MINGW*|MSYS*)
     if command -v winget >/dev/null 2>&1; then
       echo "Windows detected. Installing via winget..."
       winget install GitHub.Copilot
@@ -25,6 +26,7 @@ case "$(uname -s || echo "")" in
       exit 1
     fi
     ;;
+  *) echo "Error: Unsupported operating system $OS" >&2 ; exit 1 ;;
 esac
 
 # Detect architecture