diff --git a/gcc/config/gcn/gcn.opt b/gcc/config/gcn/gcn.opt
index 7a852c51c84..e5db6df92d7 100644
--- a/gcc/config/gcn/gcn.opt
+++ b/gcc/config/gcn/gcn.opt
@@ -44,11 +44,11 @@ EnumValue
 Enum(gpu_type) String(gfx1030) Value(PROCESSOR_GFX1030)
 
 march=
-Target RejectNegative Joined ToLower Enum(gpu_type) Var(gcn_arch) Init(PROCESSOR_FIJI)
+Target RejectNegative Negative(march=) Joined ToLower Enum(gpu_type) Var(gcn_arch) Init(PROCESSOR_FIJI)
 Specify the name of the target GPU.
 
 mtune=
-Target RejectNegative Joined ToLower Enum(gpu_type) Var(gcn_tune) Init(PROCESSOR_FIJI)
+Target RejectNegative Negative(mtune=) Joined ToLower Enum(gpu_type) Var(gcn_tune) Init(PROCESSOR_FIJI)
 Specify the name of the target GPU.
 
 m32