diff --git a/github/github.go b/github/github.go
index f3eadce9e97..2c4c8931d60 100644
--- a/github/github.go
+++ b/github/github.go
@@ -99,9 +99,6 @@ const (
 	// https://developer.github.com/changes/2017-07-17-update-topics-on-repositories/
 	mediaTypeTopicsPreview = "application/vnd.github.mercy-preview+json"
 
-	// https://developer.github.com/changes/2017-07-26-team-review-request-thor-preview/
-	mediaTypeTeamReviewPreview = "application/vnd.github.thor-preview+json"
-
 	// https://developer.github.com/v3/apps/marketplace/
 	mediaTypeMarketplacePreview = "application/vnd.github.valkyrie-preview+json"
 
diff --git a/github/pulls_reviewers.go b/github/pulls_reviewers.go
index 15b47be31fd..a1d78531506 100644
--- a/github/pulls_reviewers.go
+++ b/github/pulls_reviewers.go
@@ -32,9 +32,6 @@ func (s *PullRequestsService) RequestReviewers(ctx context.Context, owner, repo
 		return nil, nil, err
 	}
 
-	// TODO: remove custom Accept header when this API fully launches.
-	req.Header.Set("Accept", mediaTypeTeamReviewPreview)
-
 	r := new(PullRequest)
 	resp, err := s.client.Do(ctx, req, r)
 	if err != nil {
@@ -59,9 +56,6 @@ func (s *PullRequestsService) ListReviewers(ctx context.Context, owner, repo str
 		return nil, nil, err
 	}
 
-	// TODO: remove custom Accept header when this API fully launches.
-	req.Header.Set("Accept", mediaTypeTeamReviewPreview)
-
 	reviewers := new(Reviewers)
 	resp, err := s.client.Do(ctx, req, reviewers)
 	if err != nil {
@@ -81,8 +75,5 @@ func (s *PullRequestsService) RemoveReviewers(ctx context.Context, owner, repo s
 		return nil, err
 	}
 
-	// TODO: remove custom Accept header when this API fully launches.
-	req.Header.Set("Accept", mediaTypeTeamReviewPreview)
-
 	return s.client.Do(ctx, req, nil)
 }
diff --git a/github/pulls_reviewers_test.go b/github/pulls_reviewers_test.go
index 48a3bf0ceea..7c550e1bc57 100644
--- a/github/pulls_reviewers_test.go
+++ b/github/pulls_reviewers_test.go
@@ -20,7 +20,6 @@ func TestRequestReviewers(t *testing.T) {
 	mux.HandleFunc("/repos/o/r/pulls/1/requested_reviewers", func(w http.ResponseWriter, r *http.Request) {
 		testMethod(t, r, "POST")
 		testBody(t, r, `{"reviewers":["octocat","googlebot"],"team_reviewers":["justice-league","injustice-league"]}`+"\n")
-		testHeader(t, r, "Accept", mediaTypeTeamReviewPreview)
 		fmt.Fprint(w, `{"number":1}`)
 	})
 
@@ -41,7 +40,6 @@ func TestRemoveReviewers(t *testing.T) {
 
 	mux.HandleFunc("/repos/o/r/pulls/1/requested_reviewers", func(w http.ResponseWriter, r *http.Request) {
 		testMethod(t, r, "DELETE")
-		testHeader(t, r, "Accept", mediaTypeTeamReviewPreview)
 		testBody(t, r, `{"reviewers":["octocat","googlebot"],"team_reviewers":["justice-league"]}`+"\n")
 	})
 
@@ -57,7 +55,6 @@ func TestListReviewers(t *testing.T) {
 
 	mux.HandleFunc("/repos/o/r/pulls/1/requested_reviewers", func(w http.ResponseWriter, r *http.Request) {
 		testMethod(t, r, "GET")
-		testHeader(t, r, "Accept", mediaTypeTeamReviewPreview)
 		fmt.Fprint(w, `{"users":[{"login":"octocat","id":1}],"teams":[{"id":1,"name":"Justice League"}]}`)
 	})