diff --git a/bundles/org.openhab.core.auth.oauth2client/src/main/java/org/openhab/core/auth/oauth2client/internal/OAuthClientServiceImpl.java b/bundles/org.openhab.core.auth.oauth2client/src/main/java/org/openhab/core/auth/oauth2client/internal/OAuthClientServiceImpl.java
index 1d8ce4cb125..4f80799db7b 100644
--- a/bundles/org.openhab.core.auth.oauth2client/src/main/java/org/openhab/core/auth/oauth2client/internal/OAuthClientServiceImpl.java
+++ b/bundles/org.openhab.core.auth.oauth2client/src/main/java/org/openhab/core/auth/oauth2client/internal/OAuthClientServiceImpl.java
@@ -25,6 +25,7 @@
 
 import org.eclipse.jdt.annotation.NonNullByDefault;
 import org.eclipse.jdt.annotation.Nullable;
+import org.eclipse.jetty.util.Fields;
 import org.eclipse.jetty.util.UrlEncoded;
 import org.openhab.core.auth.client.oauth2.AccessTokenRefreshListener;
 import org.openhab.core.auth.client.oauth2.AccessTokenResponse;
@@ -73,6 +74,8 @@ public class OAuthClientServiceImpl implements OAuthClientService {
 
     private PersistedParams persistedParams = new PersistedParams();
 
+    private @Nullable Fields extraAuthFields = null;
+
     private volatile boolean closed = false;
 
     private OAuthClientServiceImpl(String handle, int tokenExpiresInSeconds, HttpClientFactory httpClientFactory,
@@ -157,8 +160,8 @@ public String getAuthorizationUrl(@Nullable String redirectURI, @Nullable String
         }
 
         GsonBuilder gsonBuilder = this.gsonBuilder;
-        OAuthConnector connector = gsonBuilder == null ? new OAuthConnector(httpClientFactory)
-                : new OAuthConnector(httpClientFactory, gsonBuilder);
+        OAuthConnector connector = gsonBuilder == null ? new OAuthConnector(httpClientFactory, extraAuthFields)
+                : new OAuthConnector(httpClientFactory, extraAuthFields, gsonBuilder);
         return connector.getAuthorizationUrl(authorizationUrl, clientId, redirectURI, persistedParams.state,
                 scopeToUse);
     }
@@ -213,8 +216,8 @@ public AccessTokenResponse getAccessTokenResponseByAuthorizationCode(String auth
         }
 
         GsonBuilder gsonBuilder = this.gsonBuilder;
-        OAuthConnector connector = gsonBuilder == null ? new OAuthConnector(httpClientFactory)
-                : new OAuthConnector(httpClientFactory, gsonBuilder);
+        OAuthConnector connector = gsonBuilder == null ? new OAuthConnector(httpClientFactory, extraAuthFields)
+                : new OAuthConnector(httpClientFactory, extraAuthFields, gsonBuilder);
         AccessTokenResponse accessTokenResponse = connector.grantTypeAuthorizationCode(tokenUrl, authorizationCode,
                 clientId, persistedParams.clientSecret, redirectURI,
                 Boolean.TRUE.equals(persistedParams.supportsBasicAuth));
@@ -247,8 +250,8 @@ public AccessTokenResponse getAccessTokenByResourceOwnerPasswordCredentials(Stri
         }
 
         GsonBuilder gsonBuilder = this.gsonBuilder;
-        OAuthConnector connector = gsonBuilder == null ? new OAuthConnector(httpClientFactory)
-                : new OAuthConnector(httpClientFactory, gsonBuilder);
+        OAuthConnector connector = gsonBuilder == null ? new OAuthConnector(httpClientFactory, extraAuthFields)
+                : new OAuthConnector(httpClientFactory, extraAuthFields, gsonBuilder);
         AccessTokenResponse accessTokenResponse = connector.grantTypePassword(tokenUrl, username, password,
                 persistedParams.clientId, persistedParams.clientSecret, scope,
                 Boolean.TRUE.equals(persistedParams.supportsBasicAuth));
@@ -274,8 +277,8 @@ public AccessTokenResponse getAccessTokenByClientCredentials(@Nullable String sc
         }
 
         GsonBuilder gsonBuilder = this.gsonBuilder;
-        OAuthConnector connector = gsonBuilder == null ? new OAuthConnector(httpClientFactory)
-                : new OAuthConnector(httpClientFactory, gsonBuilder);
+        OAuthConnector connector = gsonBuilder == null ? new OAuthConnector(httpClientFactory, extraAuthFields)
+                : new OAuthConnector(httpClientFactory, extraAuthFields, gsonBuilder);
         // depending on usage, cannot guarantee every parameter is not null at the beginning
         AccessTokenResponse accessTokenResponse = connector.grantTypeClientCredentials(tokenUrl, clientId,
                 persistedParams.clientSecret, scope, Boolean.TRUE.equals(persistedParams.supportsBasicAuth));
@@ -310,8 +313,8 @@ public AccessTokenResponse refreshToken() throws OAuthException, IOException, OA
         }
 
         GsonBuilder gsonBuilder = this.gsonBuilder;
-        OAuthConnector connector = gsonBuilder == null ? new OAuthConnector(httpClientFactory)
-                : new OAuthConnector(httpClientFactory, gsonBuilder);
+        OAuthConnector connector = gsonBuilder == null ? new OAuthConnector(httpClientFactory, extraAuthFields)
+                : new OAuthConnector(httpClientFactory, extraAuthFields, gsonBuilder);
         AccessTokenResponse accessTokenResponse = connector.grantTypeRefreshToken(tokenUrl,
                 lastAccessToken.getRefreshToken(), persistedParams.clientId, persistedParams.clientSecret,
                 persistedParams.scope, Boolean.TRUE.equals(persistedParams.supportsBasicAuth));
@@ -412,6 +415,19 @@ private String createNewState() {
         return UUID.randomUUID().toString();
     }
 
+    /**
+     * Adds extra fields to include in the form data when doing the token request
+     *
+     * @param key The name of the key to add to the auth form
+     * @param value The value of the new auth form param
+     */
+    public void addExtraAuthField(String key, String value) {
+        if (extraAuthFields == null) {
+            extraAuthFields = new Fields();
+        }
+        extraAuthFields.add(key, value);
+    }
+
     @Override
     public OAuthClientService withGsonBuilder(GsonBuilder gsonBuilder) {
         OAuthClientServiceImpl clientService = new OAuthClientServiceImpl(handle, persistedParams.tokenExpiresInSeconds,
diff --git a/bundles/org.openhab.core.auth.oauth2client/src/main/java/org/openhab/core/auth/oauth2client/internal/OAuthConnector.java b/bundles/org.openhab.core.auth.oauth2client/src/main/java/org/openhab/core/auth/oauth2client/internal/OAuthConnector.java
index 00d5a28d879..fd2d4fad1e5 100644
--- a/bundles/org.openhab.core.auth.oauth2client/src/main/java/org/openhab/core/auth/oauth2client/internal/OAuthConnector.java
+++ b/bundles/org.openhab.core.auth.oauth2client/src/main/java/org/openhab/core/auth/oauth2client/internal/OAuthConnector.java
@@ -63,15 +63,26 @@ public class OAuthConnector {
 
     private final HttpClientFactory httpClientFactory;
 
+    private final @Nullable Fields extraFields;
+
     private final Logger logger = LoggerFactory.getLogger(OAuthConnector.class);
     private final Gson gson;
 
     public OAuthConnector(HttpClientFactory httpClientFactory) {
-        this(httpClientFactory, new GsonBuilder());
+        this(httpClientFactory, null, new GsonBuilder());
+    }
+
+    public OAuthConnector(HttpClientFactory httpClientFactory, @Nullable Fields extraFields) {
+        this(httpClientFactory, extraFields, new GsonBuilder());
     }
 
     public OAuthConnector(HttpClientFactory httpClientFactory, GsonBuilder gsonBuilder) {
+        this(httpClientFactory, null, gsonBuilder);
+    }
+
+    public OAuthConnector(HttpClientFactory httpClientFactory, @Nullable Fields extraFields, GsonBuilder gsonBuilder) {
         this.httpClientFactory = httpClientFactory;
+        this.extraFields = extraFields;
         gson = gsonBuilder.setFieldNamingPolicy(FieldNamingPolicy.LOWER_CASE_WITH_UNDERSCORES)
                 .registerTypeAdapter(Instant.class, (JsonDeserializer<Instant>) (json, typeOfT, context) -> {
                     try {
@@ -291,6 +302,14 @@ private Fields initFields(String... parameters) {
                 fields.add(parameters[i], parameters[i + 1]);
             }
         }
+
+        if (extraFields != null) {
+            for (Fields.Field extra : extraFields) {
+                logger.debug("Oauth request (extra) parameter {}, value {}", extra.getName(), extra.getValue());
+                fields.put(extra);
+            }
+        }
+
         return fields;
     }
 
@@ -326,11 +345,12 @@ private AccessTokenResponse doRequest(final String grantType, HttpClient httpCli
             throw new IOException("Exception in oauth communication, grant type " + grantType, e);
         } catch (JsonSyntaxException e) {
             throw new OAuthException(String.format(
-                    "Unable to deserialize json into AccessTokenResponse/ OAuthResponseException. httpCode: %d json: %s",
-                    statusCode, content), e);
+                    "Unable to deserialize json into AccessTokenResponse/ OAuthResponseException. httpCode: %d json: %s: %s",
+                    statusCode, content, e.getMessage()), e);
         } catch (Exception e) {
             // Dont know what exception it is, wrap it up and throw it out
-            throw new OAuthException("Exception in oauth communication, grant type " + grantType, e);
+            throw new OAuthException(
+                    "Exception in oauth communication, grant type " + grantType + ": " + e.getMessage(), e);
         }
     }
 
diff --git a/bundles/org.openhab.core/src/main/java/org/openhab/core/auth/client/oauth2/OAuthClientService.java b/bundles/org.openhab.core/src/main/java/org/openhab/core/auth/client/oauth2/OAuthClientService.java
index 9cf6e0f02d5..54658993a43 100644
--- a/bundles/org.openhab.core/src/main/java/org/openhab/core/auth/client/oauth2/OAuthClientService.java
+++ b/bundles/org.openhab.core/src/main/java/org/openhab/core/auth/client/oauth2/OAuthClientService.java
@@ -294,6 +294,14 @@ AccessTokenResponse getAccessTokenByImplicit(@Nullable String redirectURI, @Null
      */
     boolean removeAccessTokenRefreshListener(AccessTokenRefreshListener listener);
 
+    /**
+     * Adds extra fields to include in the form data when doing the token request
+     *
+     * @param key The name of the key to add to the auth form
+     * @param value The value of the new auth form param
+     */
+    public void addExtraAuthField(String key, String value);
+
     /**
      * Adds a custom GsonBuilder to be used with the OAuth service instance.
      *