diff --git a/eval.go b/eval.go
index 07b15709..3866e0cd 100644
--- a/eval.go
+++ b/eval.go
@@ -403,7 +403,12 @@ func (e *setExpr) eval(app *app, _ []string) {
 			return
 		}
 	case "shell":
-		gOpts.shell = e.val
+		if strings.EqualFold(e.val, "cmd") {
+			// Enforce lowercase spelling to simplify special handling later.
+			gOpts.shell = "cmd"
+		} else {
+			gOpts.shell = e.val
+		}
 	case "shellflag":
 		gOpts.shellflag = e.val
 	case "shellopts":
diff --git a/os_windows.go b/os_windows.go
index ed1b5385..cbb4186b 100644
--- a/os_windows.go
+++ b/os_windows.go
@@ -123,8 +123,8 @@ func detachedCommand(name string, arg ...string) *exec.Cmd {
 }
 
 func shellCommand(s string, args []string) *exec.Cmd {
-	// Windows CMD requires special handling to deal with quoted arguments
-	if strings.ToLower(gOpts.shell) == "cmd" {
+	// Windows cmd requires special handling to deal with quoted arguments.
+	if gOpts.shell == "cmd" {
 		var builder strings.Builder
 		builder.WriteString(s)
 		for _, arg := range args {
@@ -221,8 +221,8 @@ func errCrossDevice(err error) bool {
 }
 
 func quoteString(s string) string {
-	// Windows CMD requires special handling to deal with quoted arguments
-	if strings.ToLower(gOpts.shell) == "cmd" {
+	// Windows cmd requires special handling to deal with quoted arguments.
+	if gOpts.shell == "cmd" {
 		return fmt.Sprintf(`"%s"`, s)
 	}
 	return s