diff --git a/grails-app/services/com/megatome/grails/RecaptchaService.groovy b/grails-app/services/com/megatome/grails/RecaptchaService.groovy
index 6d89515..9a9c5a6 100644
--- a/grails-app/services/com/megatome/grails/RecaptchaService.groovy
+++ b/grails-app/services/com/megatome/grails/RecaptchaService.groovy
@@ -4,6 +4,7 @@ import com.megatome.grails.recaptcha.ReCaptcha
 import com.megatome.grails.recaptcha.net.AuthenticatorProxy
 import com.megatome.grails.util.ConfigHelper
 import grails.util.Environment
+import org.grails.config.NavigableMap
 
 /**
  * Copyright 2010-2018 Megatome Technologies
@@ -24,8 +25,8 @@ import grails.util.Environment
 class RecaptchaService {
     boolean transactional = false
     def grailsApplication
-    private def recaptchaConfig = null
-    private def recap = null
+    private NavigableMap recaptchaConfig = null
+    private ReCaptcha recap = null
 
     /**
      * Gets the ReCaptcha config.
@@ -55,7 +56,7 @@ class RecaptchaService {
         return this.recaptchaConfig
     }
 
-    private def getRecaptchaInstance() {
+    private ReCaptcha getRecaptchaInstance() {
         if (!recap) {
             // Public key, private key, include noscript, include script, proxy config
             def config = getRecaptchaConfig()
@@ -76,7 +77,7 @@ class RecaptchaService {
         recap
     }
 
-    private boolean safeGetConfigValue(def value, def defaultValue) {
+    private boolean safeGetConfigValue(String value, boolean defaultValue) {
         def config = getRecaptchaConfig()
         if (config.containsKey(value)) {
             return ConfigHelper.booleanValue(config[value])
@@ -94,7 +95,7 @@ class RecaptchaService {
      *
      * @return HTML code, suitable for embedding into a webpage.
      */
-    def createCaptcha(props) {
+    String createCaptcha(props) {
         return getRecaptchaInstance().createRecaptchaHtml(props)
     }
 
@@ -105,7 +106,7 @@ class RecaptchaService {
      * @param props Options for rendering; <code>lang</code>, and <code>loadCallback</code> are currently supported by recaptcha.
      * @return HTML code, suitable for embedding into a webpage.
      */
-    def createCaptchaExplicit(props) {
+    String createCaptchaExplicit(props) {
         return getRecaptchaInstance().createRecaptchaExplicitHtml(props)
     }
 
@@ -114,7 +115,7 @@ class RecaptchaService {
      * @param props Options for rendering; <code>theme</code>, <code>type</code>, <code>tabindex</code>, <code>callback</code>, <code>expired-callback</code> are currently supported
      * @return
      */
-    def createRenderParameters(props) {
+    String createRenderParameters(props) {
         return getRecaptchaInstance().createRenderParameters(props)
     }
 
@@ -126,7 +127,7 @@ class RecaptchaService {
      *
      * @return HTML code, suitable for embedding into a webpage.
      */
-    def createScriptEntry(props) {
+    String createScriptEntry(props) {
         return getRecaptchaInstance().createScriptTag(props)
     }
 
@@ -139,7 +140,7 @@ class RecaptchaService {
      *
      * @return True if the supplied answer is correct, false otherwise. Returns true if ReCaptcha support is disabled.
      */
-    def verifyAnswer(session, remoteAddress, params) {
+    boolean verifyAnswer(session, remoteAddress, params) {
         if (!isEnabled()) {
             return true
         }
@@ -152,7 +153,7 @@ class RecaptchaService {
     /**
      * Get a value indicating if the ReCaptcha plugin should be enabled.
      */
-    def isEnabled() {
+    boolean isEnabled() {
         return safeGetConfigValue('enabled', true)
     }
 
@@ -161,7 +162,7 @@ class RecaptchaService {
      *
      * @param session The current session
      */
-    def validationFailed(session) {
+    boolean validationFailed(session) {
         return (session["recaptcha_error"] != null)
     }
 
@@ -171,7 +172,7 @@ class RecaptchaService {
      *
      * @param session The current session.
      */
-    def cleanUp(session) {
+    void cleanUp(session) {
         session["recaptcha_error"] = null
     }
 }
diff --git a/src/main/groovy/com/megatome/grails/recaptcha/net/AuthenticatorProxy.groovy b/src/main/groovy/com/megatome/grails/recaptcha/net/AuthenticatorProxy.groovy
index d020b82..e6b5411 100644
--- a/src/main/groovy/com/megatome/grails/recaptcha/net/AuthenticatorProxy.groovy
+++ b/src/main/groovy/com/megatome/grails/recaptcha/net/AuthenticatorProxy.groovy
@@ -23,7 +23,7 @@ class AuthenticatorProxy {
     int port = -1
     String username = null
     String password = null
-    private def proxy = null
+    private Proxy proxy = null
 
     public AuthenticatorProxy(Map map) {
         map.each { k,v -> if (this.hasProperty(k)) { this."$k" = v} }