diff --git a/client.go b/client.go
index 3548371..ecbfa1a 100644
--- a/client.go
+++ b/client.go
@@ -1,10 +1,11 @@
 package friendlycaptcha
 
 import (
+	"fmt"
 	"net/http"
 )
 
-type ClientOption func(*Client)
+type ClientOption func(*Client) error
 
 // A client for the Friendly Captcha API, see also the API docs at https://developer.friendlycaptcha.com
 type Client struct {
@@ -31,7 +32,7 @@ const (
 	euSiteverifyEndpointURL     = "https://eu.frcapi.com/api/v2/captcha/siteverify"
 )
 
-func NewClient(opts ...ClientOption) *Client {
+func NewClient(opts ...ClientOption) (*Client, error) {
 	const (
 		defaultSiteverifyEndpoint = globalSiteverifyEndpointURL
 	)
@@ -43,27 +44,31 @@ func NewClient(opts ...ClientOption) *Client {
 
 	// Loop through each option
 	for _, opt := range opts {
-		// Call the option giving the instantiated
-		// *Client as the argument
-		opt(c)
+		// Call the option giving the instantiated *Client as the argument
+		err := opt(c)
+		if err != nil {
+			return nil, err
+		}
 	}
 
 	if c.APIKey == "" {
-		panic("You must set your Friendly Captcha APIKey using `WithAPIKey()` when creating a new client")
+		return nil, fmt.Errorf("you must set your Friendly Captcha API key using `WithAPIKey()` when creating a new client")
 	}
 
-	return c
+	return c, nil
 }
 
 func WithAPIKey(apiKey string) ClientOption {
-	return func(c *Client) {
+	return func(c *Client) error {
 		c.APIKey = apiKey
+		return nil
 	}
 }
 
 func WithSitekey(sitekey string) ClientOption {
-	return func(c *Client) {
+	return func(c *Client) error {
 		c.Sitekey = sitekey
+		return nil
 	}
 }
 
@@ -71,8 +76,9 @@ func WithSitekey(sitekey string) ClientOption {
 //
 // This defaults to `false`.
 func WithStrictMode(strict bool) ClientOption {
-	return func(c *Client) {
+	return func(c *Client) error {
 		c.Strict = strict
+		return nil
 	}
 }
 
@@ -84,7 +90,8 @@ func WithSiteverifyEndpoint(siteverifyEndpoint string) ClientOption {
 		siteverifyEndpoint = euSiteverifyEndpointURL
 	}
 
-	return func(c *Client) {
+	return func(c *Client) error {
 		c.SiteverifyEndpoint = siteverifyEndpoint
+		return nil
 	}
 }
diff --git a/example/main.go b/example/main.go
index 192da2f..3017364 100644
--- a/example/main.go
+++ b/example/main.go
@@ -39,7 +39,11 @@ func main() {
 	if siteverifyEndpoint != "" {
 		opts = append(opts, friendlycaptcha.WithSiteverifyEndpoint(siteverifyEndpoint)) // optional, defaults to "global"
 	}
-	frcClient := friendlycaptcha.NewClient(opts...)
+	frcClient, err := friendlycaptcha.NewClient(opts...)
+	if err != nil {
+		log.Fatalf("Failed to create Friendly Captcha client: %s", err)
+	}
+
 	tmpl := template.Must(template.ParseFiles("demo.html"))
 
 	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
@@ -105,7 +109,7 @@ func main() {
 			return
 		}
 	})
-	log.Printf("Starting server on localhost port 8844 (http://localhost:8844)")
 
+	log.Printf("Starting server on localhost port 8844 (http://localhost:8844)")
 	http.ListenAndServe(":8844", nil)
 }