diff --git a/src/runtime/stack.go b/src/runtime/stack.go
index 403b3c3..821c2e8 100644
--- a/src/runtime/stack.go
+++ b/src/runtime/stack.go
@@ -66,7 +66,7 @@
 	// to each stack below the usual guard area for OS-specific
 	// purposes like signal handling. Used on Windows, Plan 9,
 	// and iOS because they do not use a separate stack.
-	_StackSystem = sys.GoosWindows*512*sys.PtrSize + sys.GoosPlan9*512 + sys.GoosDarwin*sys.GoarchArm*1024 + sys.GoosDarwin*sys.GoarchArm64*1024
+	_StackSystem = sys.GoosWindows*512*sys.PtrSize + sys.GoosPlan9*512 + sys.GoosDarwin*sys.GoarchArm64*1024
 
 	// The minimum size of stack used by Go code
 	_StackMin = 2048