diff --git a/src/flag/flag.go b/src/flag/flag.go
index 4fa502839a..bda1e1a9b8 100644
--- a/src/flag/flag.go
+++ b/src/flag/flag.go
@@ -1196,9 +1196,16 @@ func Parsed() bool {
 // CommandLine is the default set of command-line flags, parsed from [os.Args].
 // The top-level functions such as [BoolVar], [Arg], and so on are wrappers for the
 // methods of CommandLine.
-var CommandLine = NewFlagSet(os.Args[0], ExitOnError)
+var CommandLine *FlagSet
 
 func init() {
+	// It's possible for execl to hand us an empty os.Args.
+	if len(os.Args) == 0 {
+		CommandLine = NewFlagSet("", ExitOnError)
+	} else {
+		CommandLine = NewFlagSet(os.Args[0], ExitOnError)
+	}
+
 	// Override generic FlagSet default Usage with call to global Usage.
 	// Note: This is not CommandLine.Usage = Usage,
 	// because we want any eventual call to use any updated value of Usage,