diff --git a/oidc/config.go b/oidc/config.go
index f782e81..4f24b37 100644
--- a/oidc/config.go
+++ b/oidc/config.go
@@ -288,7 +288,7 @@ func (c *Config) Validate() error {
 		}
 	}
 	if c.ProviderCA != "" && c.RoundTripper != nil {
-		return fmt.Errorf("%s: you cannot specify both a ProviderCA and Transport: %w", op, ErrInvalidParameter)
+		return fmt.Errorf("%s: you cannot specify both a ProviderCA and RoundTripper: %w", op, ErrInvalidParameter)
 	}
 
 	if c.ProviderConfig != nil {
diff --git a/oidc/provider.go b/oidc/provider.go
index d03b2e7..f8b342e 100644
--- a/oidc/provider.go
+++ b/oidc/provider.go
@@ -639,7 +639,7 @@ func (p *Provider) HTTPClient() (*http.Client, error) {
 
 	switch {
 	case p.config.RoundTripper != nil && p.config.ProviderCA != "":
-		return nil, fmt.Errorf("%s: you cannot specify config for both a ProviderCA and Transport: %w", op, ErrInvalidParameter)
+		return nil, fmt.Errorf("%s: you cannot specify config for both a ProviderCA and RoundTripper: %w", op, ErrInvalidParameter)
 	case p.config.ProviderCA != "":
 		certPool := x509.NewCertPool()
 		if ok := certPool.AppendCertsFromPEM([]byte(p.config.ProviderCA)); !ok {
diff --git a/oidc/provider_test.go b/oidc/provider_test.go
index 8dca1dd..b07b128 100644
--- a/oidc/provider_test.go
+++ b/oidc/provider_test.go
@@ -737,7 +737,7 @@ func TestHTTPClient(t *testing.T) {
 		_, err := p.HTTPClient()
 		require.Error(t, err)
 		assert.ErrorIs(t, err, ErrInvalidParameter)
-		assert.ErrorContains(t, err, "you cannot specify config for both a ProviderCA and Transport")
+		assert.ErrorContains(t, err, "you cannot specify config for both a ProviderCA and RoundTripper")
 	})
 }