diff --git a/.golangci.yml b/.golangci.yml
index 2f9b8162..eece6318 100644
--- a/.golangci.yml
+++ b/.golangci.yml
@@ -50,6 +50,7 @@ linters:
     - lll               # don't want hard limits for line length
     - maintidx          # covered by gocyclo
     - maligned          # readability trumps efficient struct packing
+    - mnd               # status codes are clearer than constants
     - nlreturn          # generous whitespace violates house style
     - nonamedreturns    # named returns are fine; it's *bare* returns that are bad
     - nosnakecase       # deprecated in https://github.com/golangci/golangci-lint/pull/3065
@@ -64,7 +65,7 @@ issues:
   exclude:
     # Don't ban use of fmt.Errorf to create new errors, but the remaining
     # checks from err113 are useful.
-    - "err113: do not define dynamic errors.*"
+    - "do not define dynamic errors, use wrapped static errors instead: .*"
 
   exclude-rules:
     # If future reflect.Kinds are nil-able, we'll find out when a test fails.
@@ -129,3 +130,6 @@ issues:
     # Allow fmt.Sprintf for cmd/protoc-gen-connect-go for consistency
     - linters: [perfsprint]
       path: cmd/protoc-gen-connect-go/main.go
+    # Allow non-canonical headers in tests
+    - linters: [canonicalheader]
+      path: protocol_grpc_test.go
diff --git a/client_stream_test.go b/client_stream_test.go
index a812caa1..cf072392 100644
--- a/client_stream_test.go
+++ b/client_stream_test.go
@@ -95,8 +95,8 @@ func verifyHeaders(t *testing.T, headers http.Header) {
 	assert.Equal(t, headers, http.Header{})
 
 	// Verify set/del don't panic
-	headers.Set("a", "b")
-	headers.Del("a")
+	headers.Set("A", "b")
+	headers.Del("A")
 }
 
 type nopStreamingClientConn struct {
diff --git a/error_test.go b/error_test.go
index 93306a9c..3535b0b0 100644
--- a/error_test.go
+++ b/error_test.go
@@ -39,8 +39,8 @@ func TestErrorNilUnderlying(t *testing.T) {
 	err.AddDetail(detail)
 	assert.Equal(t, len(err.Details()), 1)
 	assert.Equal(t, err.Details()[0].Type(), "google.protobuf.Empty")
-	err.Meta().Set("foo", "bar")
-	assert.Equal(t, err.Meta().Get("foo"), "bar")
+	err.Meta().Set("Foo", "bar")
+	assert.Equal(t, err.Meta().Get("Foo"), "bar")
 	assert.Equal(t, CodeOf(err), CodeUnknown)
 }
 
@@ -51,9 +51,9 @@ func TestErrorFormatting(t *testing.T) {
 		NewError(CodeUnavailable, errors.New("")).Error(),
 		CodeUnavailable.String(),
 	)
-	got := NewError(CodeUnavailable, errors.New("foo")).Error()
+	got := NewError(CodeUnavailable, errors.New("Foo")).Error()
 	assert.True(t, strings.Contains(got, CodeUnavailable.String()))
-	assert.True(t, strings.Contains(got, "foo"))
+	assert.True(t, strings.Contains(got, "Foo"))
 }
 
 func TestErrorCode(t *testing.T) {
diff --git a/protocol_connect.go b/protocol_connect.go
index 26f18b06..45577d82 100644
--- a/protocol_connect.go
+++ b/protocol_connect.go
@@ -1018,7 +1018,8 @@ func (m *connectUnaryRequestMarshaler) marshalWithGet(message any) *Error {
 	if !isTooBig {
 		url := m.buildGetURL(data, false /* compressed */)
 		if m.getURLMaxBytes <= 0 || len(url.String()) < m.getURLMaxBytes {
-			return m.writeWithGet(url)
+			m.writeWithGet(url)
+			return nil
 		}
 		if m.compressionPool == nil {
 			if m.getUseFallback {
@@ -1044,7 +1045,8 @@ func (m *connectUnaryRequestMarshaler) marshalWithGet(message any) *Error {
 	}
 	url := m.buildGetURL(compressed.Bytes(), true /* compressed */)
 	if m.getURLMaxBytes <= 0 || len(url.String()) < m.getURLMaxBytes {
-		return m.writeWithGet(url)
+		m.writeWithGet(url)
+		return nil
 	}
 	if m.getUseFallback {
 		setHeaderCanonical(m.header, connectUnaryHeaderCompression, m.compressionName)
@@ -1071,14 +1073,13 @@ func (m *connectUnaryRequestMarshaler) buildGetURL(data []byte, compressed bool)
 	return &url
 }
 
-func (m *connectUnaryRequestMarshaler) writeWithGet(url *url.URL) *Error {
+func (m *connectUnaryRequestMarshaler) writeWithGet(url *url.URL) {
 	delHeaderCanonical(m.header, connectHeaderProtocolVersion)
 	delHeaderCanonical(m.header, headerContentType)
 	delHeaderCanonical(m.header, headerContentEncoding)
 	delHeaderCanonical(m.header, headerContentLength)
 	m.duplexCall.SetMethod(http.MethodGet)
 	*m.duplexCall.URL() = *url
-	return nil
 }
 
 type connectUnaryUnmarshaler struct {