diff --git a/cert_error_go119.go b/cert_error_go119.go
new file mode 100644
index 0000000..b2b27e8
--- /dev/null
+++ b/cert_error_go119.go
@@ -0,0 +1,14 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: MPL-2.0
+
+//go:build !go1.20
+// +build !go1.20
+
+package retryablehttp
+
+import "crypto/x509"
+
+func isCertError(err error) bool {
+	_, ok := err.(x509.UnknownAuthorityError)
+	return ok
+}
diff --git a/cert_error_go120.go b/cert_error_go120.go
new file mode 100644
index 0000000..a3cd315
--- /dev/null
+++ b/cert_error_go120.go
@@ -0,0 +1,14 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: MPL-2.0
+
+//go:build go1.20
+// +build go1.20
+
+package retryablehttp
+
+import "crypto/tls"
+
+func isCertError(err error) bool {
+	_, ok := err.(*tls.CertificateVerificationError)
+	return ok
+}
diff --git a/client.go b/client.go
index f69063c..12ac50b 100644
--- a/client.go
+++ b/client.go
@@ -27,7 +27,6 @@ package retryablehttp
 import (
 	"bytes"
 	"context"
-	"crypto/x509"
 	"fmt"
 	"io"
 	"log"
@@ -62,6 +61,10 @@ var (
 	// limit the size we consume to respReadLimit.
 	respReadLimit = int64(4096)
 
+	// timeNow sets the function that returns the current time.
+	// This defaults to time.Now. Changes to this should only be done in tests.
+	timeNow = time.Now
+
 	// A regular expression to match the error returned by net/http when the
 	// configured number of redirects is exhausted. This error isn't typed
 	// specifically so we resort to matching on the error string.
@@ -72,9 +75,10 @@ var (
 	// specifically so we resort to matching on the error string.
 	schemeErrorRe = regexp.MustCompile(`unsupported protocol scheme`)
 
-	// timeNow sets the function that returns the current time.
-	// This defaults to time.Now. Changes to this should only be done in tests.
-	timeNow = time.Now
+	// A regular expression to match the error returned by net/http when a
+	// request header or value is invalid. This error isn't typed
+	// specifically so we resort to matching on the error string.
+	invalidHeaderErrorRe = regexp.MustCompile(`invalid header`)
 
 	// A regular expression to match the error returned by net/http when the
 	// TLS certificate is not trusted. This error isn't typed
@@ -501,11 +505,16 @@ func baseRetryPolicy(resp *http.Response, err error) (bool, error) {
 				return false, v
 			}
 
+			// Don't retry if the error was due to an invalid header.
+			if invalidHeaderErrorRe.MatchString(v.Error()) {
+				return false, v
+			}
+
 			// Don't retry if the error was due to TLS cert verification failure.
 			if notTrustedErrorRe.MatchString(v.Error()) {
 				return false, v
 			}
-			if _, ok := v.Err.(x509.UnknownAuthorityError); ok {
+			if isCertError(v.Err) {
 				return false, v
 			}
 		}
diff --git a/client_test.go b/client_test.go
index 3cba8ec..3c37ef6 100644
--- a/client_test.go
+++ b/client_test.go
@@ -935,6 +935,60 @@ func TestClient_DefaultRetryPolicy_invalidscheme(t *testing.T) {
 	}
 }
 
+func TestClient_DefaultRetryPolicy_invalidheadername(t *testing.T) {
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(200)
+	}))
+	defer ts.Close()
+
+	attempts := 0
+	client := NewClient()
+	client.CheckRetry = func(_ context.Context, resp *http.Response, err error) (bool, error) {
+		attempts++
+		return DefaultRetryPolicy(context.TODO(), resp, err)
+	}
+
+	req, err := http.NewRequest(http.MethodGet, ts.URL, nil)
+	if err != nil {
+		t.Fatalf("err: %v", err)
+	}
+	req.Header.Set("Header-Name-\033", "header value")
+	_, err = client.StandardClient().Do(req)
+	if err == nil {
+		t.Fatalf("expected header error, got nil")
+	}
+	if attempts != 1 {
+		t.Fatalf("expected 1 attempt, got %d", attempts)
+	}
+}
+
+func TestClient_DefaultRetryPolicy_invalidheadervalue(t *testing.T) {
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(200)
+	}))
+	defer ts.Close()
+
+	attempts := 0
+	client := NewClient()
+	client.CheckRetry = func(_ context.Context, resp *http.Response, err error) (bool, error) {
+		attempts++
+		return DefaultRetryPolicy(context.TODO(), resp, err)
+	}
+
+	req, err := http.NewRequest(http.MethodGet, ts.URL, nil)
+	if err != nil {
+		t.Fatalf("err: %v", err)
+	}
+	req.Header.Set("Header-Name", "bad header value \033")
+	_, err = client.StandardClient().Do(req)
+	if err == nil {
+		t.Fatalf("expected header value error, got nil")
+	}
+	if attempts != 1 {
+		t.Fatalf("expected 1 attempt, got %d", attempts)
+	}
+}
+
 func TestClient_CheckRetryStop(t *testing.T) {
 	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		http.Error(w, "test_500_body", http.StatusInternalServerError)