diff --git a/graphql/handler/transport/headers_test.go b/graphql/handler/transport/headers_test.go
index 5e8160861a2..c599c929359 100644
--- a/graphql/handler/transport/headers_test.go
+++ b/graphql/handler/transport/headers_test.go
@@ -21,7 +21,7 @@ func TestHeadersWithPOST(t *testing.T) {
 		h := testserver.New()
 		h.AddTransport(transport.POST{})
 
-		resp := doRequest(h, "POST", "/graphql", `{"query":"{ name }"}`)
+		resp := doRequest(h, "POST", "/graphql", `{"query":"{ name }"}`, "application/json")
 		assert.Equal(t, http.StatusOK, resp.Code)
 		assert.Equal(t, 1, len(resp.Header()))
 		assert.Equal(t, "application/json", resp.Header().Get("Content-Type"))
@@ -36,7 +36,7 @@ func TestHeadersWithPOST(t *testing.T) {
 		h := testserver.New()
 		h.AddTransport(transport.POST{ResponseHeaders: headers})
 
-		resp := doRequest(h, "POST", "/graphql", `{"query":"{ name }"}`)
+		resp := doRequest(h, "POST", "/graphql", `{"query":"{ name }"}`, "application/json")
 		assert.Equal(t, http.StatusOK, resp.Code)
 		assert.Equal(t, 2, len(resp.Header()))
 		assert.Equal(t, "application/json; charset: utf8", resp.Header().Get("Content-Type"))
@@ -50,7 +50,7 @@ func TestHeadersWithGET(t *testing.T) {
 		h := testserver.New()
 		h.AddTransport(transport.GET{})
 
-		resp := doRequest(h, "GET", "/graphql?query={name}", "")
+		resp := doRequest(h, "GET", "/graphql?query={name}", "", "application/json")
 		assert.Equal(t, http.StatusOK, resp.Code)
 		assert.Equal(t, 1, len(resp.Header()))
 		assert.Equal(t, "application/json", resp.Header().Get("Content-Type"))
@@ -65,7 +65,7 @@ func TestHeadersWithGET(t *testing.T) {
 		h := testserver.New()
 		h.AddTransport(transport.GET{ResponseHeaders: headers})
 
-		resp := doRequest(h, "GET", "/graphql?query={name}", "")
+		resp := doRequest(h, "GET", "/graphql?query={name}", "", "application/json")
 		assert.Equal(t, http.StatusOK, resp.Code)
 		assert.Equal(t, 2, len(resp.Header()))
 		assert.Equal(t, "application/json; charset: utf8", resp.Header().Get("Content-Type"))
@@ -73,6 +73,34 @@ func TestHeadersWithGET(t *testing.T) {
 	})
 }
 
+func TestHeadersWithGRAPHQL(t *testing.T) {
+	t.Run("Headers not set", func(t *testing.T) {
+		h := testserver.New()
+		h.AddTransport(transport.GRAPHQL{})
+
+		resp := doRequest(h, "POST", "/graphql", `{ name }`, "application/graphql")
+		assert.Equal(t, http.StatusOK, resp.Code)
+		assert.Equal(t, 1, len(resp.Header()))
+		assert.Equal(t, "application/json", resp.Header().Get("Content-Type"))
+	})
+
+	t.Run("Headers set", func(t *testing.T) {
+		headers := map[string][]string{
+			"Content-Type": {"application/json; charset: utf8"},
+			"Other-Header": {"dummy-get-qraphql"},
+		}
+
+		h := testserver.New()
+		h.AddTransport(transport.GRAPHQL{ResponseHeaders: headers})
+
+		resp := doRequest(h, "POST", "/graphql", `{ name }`, "application/graphql")
+		assert.Equal(t, http.StatusOK, resp.Code)
+		assert.Equal(t, 2, len(resp.Header()))
+		assert.Equal(t, "application/json; charset: utf8", resp.Header().Get("Content-Type"))
+		assert.Equal(t, "dummy-get-qraphql", resp.Header().Get("Other-Header"))
+	})
+}
+
 func TestHeadersWithMULTIPART(t *testing.T) {
 	t.Run("Headers not set", func(t *testing.T) {
 		es := &graphql.ExecutableSchemaMock{
diff --git a/graphql/handler/transport/http_get_test.go b/graphql/handler/transport/http_get_test.go
index 307b2b90357..5e46d231855 100644
--- a/graphql/handler/transport/http_get_test.go
+++ b/graphql/handler/transport/http_get_test.go
@@ -14,36 +14,36 @@ func TestGET(t *testing.T) {
 	h.AddTransport(transport.GET{})
 
 	t.Run("success", func(t *testing.T) {
-		resp := doRequest(h, "GET", "/graphql?query={name}", ``)
+		resp := doRequest(h, "GET", "/graphql?query={name}", ``, "application/json")
 		assert.Equal(t, http.StatusOK, resp.Code, resp.Body.String())
 		assert.Equal(t, `{"data":{"name":"test"}}`, resp.Body.String())
 	})
 
 	t.Run("has json content-type header", func(t *testing.T) {
-		resp := doRequest(h, "GET", "/graphql?query={name}", ``)
+		resp := doRequest(h, "GET", "/graphql?query={name}", ``, "application/json")
 		assert.Equal(t, "application/json", resp.Header().Get("Content-Type"))
 	})
 
 	t.Run("decode failure", func(t *testing.T) {
-		resp := doRequest(h, "GET", "/graphql?query={name}&variables=notjson", "")
+		resp := doRequest(h, "GET", "/graphql?query={name}&variables=notjson", "", "application/json")
 		assert.Equal(t, http.StatusBadRequest, resp.Code, resp.Body.String())
 		assert.Equal(t, `{"errors":[{"message":"variables could not be decoded"}],"data":null}`, resp.Body.String())
 	})
 
 	t.Run("invalid variable", func(t *testing.T) {
-		resp := doRequest(h, "GET", `/graphql?query=query($id:Int!){find(id:$id)}&variables={"id":false}`, "")
+		resp := doRequest(h, "GET", `/graphql?query=query($id:Int!){find(id:$id)}&variables={"id":false}`, "", "application/json")
 		assert.Equal(t, http.StatusUnprocessableEntity, resp.Code, resp.Body.String())
 		assert.Equal(t, `{"errors":[{"message":"cannot use bool as Int","path":["variable","id"],"extensions":{"code":"GRAPHQL_VALIDATION_FAILED"}}],"data":null}`, resp.Body.String())
 	})
 
 	t.Run("parse failure", func(t *testing.T) {
-		resp := doRequest(h, "GET", "/graphql?query=!", "")
+		resp := doRequest(h, "GET", "/graphql?query=!", "", "application/json")
 		assert.Equal(t, http.StatusUnprocessableEntity, resp.Code, resp.Body.String())
 		assert.Equal(t, `{"errors":[{"message":"Unexpected !","locations":[{"line":1,"column":1}],"extensions":{"code":"GRAPHQL_PARSE_FAILED"}}],"data":null}`, resp.Body.String())
 	})
 
 	t.Run("no mutations", func(t *testing.T) {
-		resp := doRequest(h, "GET", "/graphql?query=mutation{name}", "")
+		resp := doRequest(h, "GET", "/graphql?query=mutation{name}", "", "application/json")
 		assert.Equal(t, http.StatusNotAcceptable, resp.Code, resp.Body.String())
 		assert.Equal(t, `{"errors":[{"message":"GET requests only allow query operations"}],"data":null}`, resp.Body.String())
 	})
diff --git a/graphql/handler/transport/http_post_test.go b/graphql/handler/transport/http_post_test.go
index b104118e6fd..a26ba12912e 100644
--- a/graphql/handler/transport/http_post_test.go
+++ b/graphql/handler/transport/http_post_test.go
@@ -17,41 +17,41 @@ func TestPOST(t *testing.T) {
 	h.AddTransport(transport.POST{})
 
 	t.Run("success", func(t *testing.T) {
-		resp := doRequest(h, "POST", "/graphql", `{"query":"{ name }"}`)
+		resp := doRequest(h, "POST", "/graphql", `{"query":"{ name }"}`, "application/json")
 		assert.Equal(t, http.StatusOK, resp.Code)
 		assert.Equal(t, `{"data":{"name":"test"}}`, resp.Body.String())
 	})
 
 	t.Run("decode failure", func(t *testing.T) {
-		resp := doRequest(h, "POST", "/graphql", "notjson")
+		resp := doRequest(h, "POST", "/graphql", "notjson", "application/json")
 		assert.Equal(t, http.StatusBadRequest, resp.Code, resp.Body.String())
 		assert.Equal(t, resp.Header().Get("Content-Type"), "application/json")
 		assert.Equal(t, `{"errors":[{"message":"json request body could not be decoded: invalid character 'o' in literal null (expecting 'u') body:notjson"}],"data":null}`, resp.Body.String())
 	})
 
 	t.Run("parse failure", func(t *testing.T) {
-		resp := doRequest(h, "POST", "/graphql", `{"query": "!"}`)
+		resp := doRequest(h, "POST", "/graphql", `{"query": "!"}`, "application/json")
 		assert.Equal(t, http.StatusUnprocessableEntity, resp.Code, resp.Body.String())
 		assert.Equal(t, resp.Header().Get("Content-Type"), "application/json")
 		assert.Equal(t, `{"errors":[{"message":"Unexpected !","locations":[{"line":1,"column":1}],"extensions":{"code":"GRAPHQL_PARSE_FAILED"}}],"data":null}`, resp.Body.String())
 	})
 
 	t.Run("validation failure", func(t *testing.T) {
-		resp := doRequest(h, "POST", "/graphql", `{"query": "{ title }"}`)
+		resp := doRequest(h, "POST", "/graphql", `{"query": "{ title }"}`, "application/json")
 		assert.Equal(t, http.StatusUnprocessableEntity, resp.Code, resp.Body.String())
 		assert.Equal(t, resp.Header().Get("Content-Type"), "application/json")
 		assert.Equal(t, `{"errors":[{"message":"Cannot query field \"title\" on type \"Query\".","locations":[{"line":1,"column":3}],"extensions":{"code":"GRAPHQL_VALIDATION_FAILED"}}],"data":null}`, resp.Body.String())
 	})
 
 	t.Run("invalid variable", func(t *testing.T) {
-		resp := doRequest(h, "POST", "/graphql", `{"query": "query($id:Int!){find(id:$id)}","variables":{"id":false}}`)
+		resp := doRequest(h, "POST", "/graphql", `{"query": "query($id:Int!){find(id:$id)}","variables":{"id":false}}`, "application/json")
 		assert.Equal(t, http.StatusUnprocessableEntity, resp.Code, resp.Body.String())
 		assert.Equal(t, resp.Header().Get("Content-Type"), "application/json")
 		assert.Equal(t, `{"errors":[{"message":"cannot use bool as Int","path":["variable","id"],"extensions":{"code":"GRAPHQL_VALIDATION_FAILED"}}],"data":null}`, resp.Body.String())
 	})
 
 	t.Run("execution failure", func(t *testing.T) {
-		resp := doRequest(h, "POST", "/graphql", `{"query": "mutation { name }"}`)
+		resp := doRequest(h, "POST", "/graphql", `{"query": "mutation { name }"}`, "application/json")
 		assert.Equal(t, http.StatusOK, resp.Code, resp.Body.String())
 		assert.Equal(t, resp.Header().Get("Content-Type"), "application/json")
 		assert.Equal(t, `{"errors":[{"message":"mutations are not supported"}],"data":null}`, resp.Body.String())
@@ -85,10 +85,6 @@ func TestPOST(t *testing.T) {
 		invalidContentTypes := []string{
 			"",
 			"text/plain",
-
-			// These content types are currently not supported, but they are supported by other GraphQL servers, like express-graphql.
-			"application/x-www-form-urlencoded",
-			"application/graphql",
 		}
 
 		for _, tc := range invalidContentTypes {
@@ -101,9 +97,9 @@ func TestPOST(t *testing.T) {
 	})
 }
 
-func doRequest(handler http.Handler, method string, target string, body string) *httptest.ResponseRecorder {
+func doRequest(handler http.Handler, method string, target string, body string, contentType string) *httptest.ResponseRecorder {
 	r := httptest.NewRequest(method, target, strings.NewReader(body))
-	r.Header.Set("Content-Type", "application/json")
+	r.Header.Set("Content-Type", contentType)
 	w := httptest.NewRecorder()
 
 	handler.ServeHTTP(w, r)
diff --git a/graphql/handler/transport/options_test.go b/graphql/handler/transport/options_test.go
index fee62752126..f0812c58fb4 100644
--- a/graphql/handler/transport/options_test.go
+++ b/graphql/handler/transport/options_test.go
@@ -14,7 +14,7 @@ func TestOptions(t *testing.T) {
 	t.Run("responds to options requests with default methods", func(t *testing.T) {
 		h := testserver.New()
 		h.AddTransport(transport.Options{})
-		resp := doRequest(h, "OPTIONS", "/graphql?query={me{name}}", ``)
+		resp := doRequest(h, "OPTIONS", "/graphql?query={me{name}}", ``, "application/json")
 		assert.Equal(t, http.StatusOK, resp.Code)
 		assert.Equal(t, "OPTIONS, GET, POST", resp.Header().Get("Allow"))
 	})
@@ -24,7 +24,7 @@ func TestOptions(t *testing.T) {
 		h.AddTransport(transport.Options{
 			AllowedMethods: []string{http.MethodOptions, http.MethodPost, http.MethodHead},
 		})
-		resp := doRequest(h, "OPTIONS", "/graphql?query={me{name}}", ``)
+		resp := doRequest(h, "OPTIONS", "/graphql?query={me{name}}", ``, "application/json")
 		assert.Equal(t, http.StatusOK, resp.Code)
 		assert.Equal(t, "OPTIONS, POST, HEAD", resp.Header().Get("Allow"))
 	})
@@ -32,7 +32,7 @@ func TestOptions(t *testing.T) {
 	t.Run("responds to head requests", func(t *testing.T) {
 		h := testserver.New()
 		h.AddTransport(transport.Options{})
-		resp := doRequest(h, "HEAD", "/graphql?query={me{name}}", ``)
+		resp := doRequest(h, "HEAD", "/graphql?query={me{name}}", ``, "application/json")
 		assert.Equal(t, http.StatusMethodNotAllowed, resp.Code)
 	})
 }