diff --git a/internal/witness/client/http/witness_client.go b/internal/witness/client/http/witness_client.go
index a04f55ff23..1a836d26d4 100644
--- a/internal/witness/client/http/witness_client.go
+++ b/internal/witness/client/http/witness_client.go
@@ -43,7 +43,7 @@ func (w Witness) GetLatestSTH(ctx context.Context, logID string) ([]byte, error)
 	if err != nil {
 		return nil, fmt.Errorf("failed to parse URL: %v", err)
 	}
-	req, err := http.NewRequest("GET", u.String(), nil)
+	req, err := http.NewRequest(http.MethodGet, u.String(), nil)
 	if err != nil {
 		return nil, fmt.Errorf("failed to create request: %v", err)
 	}
@@ -75,7 +75,7 @@ func (w Witness) Update(ctx context.Context, logID string, sth []byte, proof [][
 	if err != nil {
 		return nil, fmt.Errorf("failed to parse URL: %v", err)
 	}
-	req, err := http.NewRequest("PUT", u.String(), bytes.NewReader(reqBody))
+	req, err := http.NewRequest(http.MethodPut, u.String(), bytes.NewReader(reqBody))
 	if err != nil {
 		return nil, fmt.Errorf("failed to create request: %v", err)
 	}
diff --git a/jsonclient/client.go b/jsonclient/client.go
index a95f19ccdc..7e7cb7279e 100644
--- a/jsonclient/client.go
+++ b/jsonclient/client.go
@@ -248,6 +248,10 @@ func (c *JSONClient) PostAndParse(ctx context.Context, path string, req, rsp int
 		}
 		return nil, nil, err
 	}
+	if httpRsp.Request.Method != http.MethodPost {
+		// https://developer.mozilla.org/en-US/docs/Web/HTTP/Redirections#permanent_redirections
+		return nil, nil, fmt.Errorf("POST request to %q was converted to %s request to %q", fullURI, httpRsp.Request.Method, httpRsp.Request.URL)
+	}
 
 	if httpRsp.StatusCode == http.StatusOK {
 		if err = json.Unmarshal(body, &rsp); err != nil {
diff --git a/trillian/ctfe/handlers_test.go b/trillian/ctfe/handlers_test.go
index abf485ca14..bc786409a0 100644
--- a/trillian/ctfe/handlers_test.go
+++ b/trillian/ctfe/handlers_test.go
@@ -311,7 +311,7 @@ func TestGetRoots(t *testing.T) {
 	defer info.mockCtrl.Finish()
 	handler := AppHandler{Info: info.li, Handler: getRoots, Name: "GetRoots", Method: http.MethodGet}
 
-	req, err := http.NewRequest("GET", "http://example.com/ct/v1/get-roots", nil)
+	req, err := http.NewRequest(http.MethodGet, "http://example.com/ct/v1/get-roots", nil)
 	if err != nil {
 		t.Fatalf("Failed to create request: %v", err)
 	}
@@ -420,7 +420,7 @@ func TestAddChainWhitespace(t *testing.T) {
 
 			recorder := httptest.NewRecorder()
 			handler := AppHandler{Info: info.li, Handler: addChain, Name: "AddChain", Method: http.MethodPost}
-			req, err := http.NewRequest("POST", "http://example.com/ct/v1/add-chain", strings.NewReader(test.body))
+			req, err := http.NewRequest(http.MethodPost, "http://example.com/ct/v1/add-chain", strings.NewReader(test.body))
 			if err != nil {
 				t.Fatalf("Failed to create POST request: %v", err)
 			}
@@ -775,7 +775,7 @@ func TestGetSTH(t *testing.T) {
 				srReq.ChargeTo = &trillian.ChargeTo{User: []string{test.wantQuotaUser}}
 			}
 			info.client.EXPECT().GetLatestSignedLogRoot(deadlineMatcher(), cmpMatcher{srReq}).Return(test.rpcRsp, test.rpcErr)
-			req, err := http.NewRequest("GET", "http://example.com/ct/v1/get-sth", nil)
+			req, err := http.NewRequest(http.MethodGet, "http://example.com/ct/v1/get-sth", nil)
 			if err != nil {
 				t.Errorf("Failed to create request: %v", err)
 				return
@@ -1010,7 +1010,7 @@ func TestGetEntries(t *testing.T) {
 		info.setRemoteQuotaUser(test.wantQuotaUser)
 		handler := AppHandler{Info: info.li, Handler: getEntries, Name: "GetEntries", Method: http.MethodGet}
 		path := fmt.Sprintf("/ct/v1/get-entries?%s", test.req)
-		req, err := http.NewRequest("GET", path, nil)
+		req, err := http.NewRequest(http.MethodGet, path, nil)
 		if err != nil {
 			t.Errorf("Failed to create request: %v", err)
 			continue
@@ -1187,7 +1187,7 @@ func TestGetEntriesRanges(t *testing.T) {
 			}
 
 			path := fmt.Sprintf("/ct/v1/get-entries?start=%d&end=%d", test.start, test.end)
-			req, err := http.NewRequest("GET", path, nil)
+			req, err := http.NewRequest(http.MethodGet, path, nil)
 			if err != nil {
 				t.Fatalf("Failed to create request: %v", err)
 			}
@@ -1444,7 +1444,7 @@ func TestGetProofByHash(t *testing.T) {
 
 	for _, test := range tests {
 		info.setRemoteQuotaUser(test.wantQuotaUser)
-		req, err := http.NewRequest("GET", fmt.Sprintf("/ct/v1/proof-by-hash?%s", test.req), nil)
+		req, err := http.NewRequest(http.MethodGet, fmt.Sprintf("/ct/v1/proof-by-hash?%s", test.req), nil)
 		if err != nil {
 			t.Errorf("Failed to create request: %v", err)
 			continue
@@ -1792,7 +1792,7 @@ func TestGetSTHConsistency(t *testing.T) {
 
 	for _, test := range tests {
 		info.setRemoteQuotaUser(test.wantQuotaUser)
-		req, err := http.NewRequest("GET", fmt.Sprintf("/ct/v1/get-sth-consistency?%s", test.req), nil)
+		req, err := http.NewRequest(http.MethodGet, fmt.Sprintf("/ct/v1/get-sth-consistency?%s", test.req), nil)
 		if err != nil {
 			t.Errorf("Failed to create request: %v", err)
 			continue
@@ -2126,7 +2126,7 @@ func TestGetEntryAndProof(t *testing.T) {
 
 	for _, test := range tests {
 		info.setRemoteQuotaUser(test.wantQuotaUser)
-		req, err := http.NewRequest("GET", fmt.Sprintf("/ct/v1/get-entry-and-proof?%s", test.req), nil)
+		req, err := http.NewRequest(http.MethodGet, fmt.Sprintf("/ct/v1/get-entry-and-proof?%s", test.req), nil)
 		if err != nil {
 			t.Errorf("Failed to create request: %v", err)
 			continue
@@ -2250,7 +2250,7 @@ func makeAddChainRequest(t *testing.T, li *logInfo, body io.Reader) *httptest.Re
 
 func makeAddChainRequestInternal(t *testing.T, handler AppHandler, path string, body io.Reader) *httptest.ResponseRecorder {
 	t.Helper()
-	req, err := http.NewRequest("POST", fmt.Sprintf("http://example.com/ct/v1/%s", path), body)
+	req, err := http.NewRequest(http.MethodPost, fmt.Sprintf("http://example.com/ct/v1/%s", path), body)
 	if err != nil {
 		t.Fatalf("Failed to create POST request: %v", err)
 	}