diff --git a/pkg/apis/dra/v1beta1/api.pb.go b/pkg/apis/dra/v1beta1/api.pb.go
index 2f024c6..4d84e53 100644
--- a/pkg/apis/dra/v1beta1/api.pb.go
+++ b/pkg/apis/dra/v1beta1/api.pb.go
@@ -326,7 +326,8 @@ func (m *NodeUnprepareResourcesRequest) GetClaims() []*Claim {
 type NodeUnprepareResourcesResponse struct {
 	// The ResourceClaims for which preparation was reverted.
 	// The same rules as for NodePrepareResourcesResponse.claims
-	// apply.
+	// apply. In particular, all claims in the request must
+	// have an entry in the response, even if that entry is nil.
 	Claims               map[string]*NodeUnprepareResourceResponse `protobuf:"bytes,1,rep,name=claims,proto3" json:"claims,omitempty" protobuf_key:"bytes,1,opt,name=key,proto3" protobuf_val:"bytes,2,opt,name=value,proto3"`
 	XXX_NoUnkeyedLiteral struct{}                                  `json:"-"`
 	XXX_sizecache        int32                                     `json:"-"`
diff --git a/pkg/apis/dra/v1beta1/api.proto b/pkg/apis/dra/v1beta1/api.proto
index 8afd10a..e2f7960 100644
--- a/pkg/apis/dra/v1beta1/api.proto
+++ b/pkg/apis/dra/v1beta1/api.proto
@@ -95,7 +95,8 @@ message NodeUnprepareResourcesRequest {
 message NodeUnprepareResourcesResponse {
     // The ResourceClaims for which preparation was reverted.
     // The same rules as for NodePrepareResourcesResponse.claims
-    // apply.
+    // apply. In particular, all claims in the request must
+    // have an entry in the response, even if that entry is nil.
     map<string, NodeUnprepareResourceResponse> claims = 1;
 }