diff --git a/cc/builder.go b/cc/builder.go
index b494f7b..8d2cb3b 100644
--- a/cc/builder.go
+++ b/cc/builder.go
@@ -746,7 +746,7 @@
 	arCmd := "${config.ClangBin}/llvm-ar"
 	arFlags := ""
 	if !ctx.Darwin() {
-		arFlags += " -format=gnu"
+		arFlags += " --format=gnu"
 	}
 
 	if len(wholeStaticLibs) == 0 {