diff --git a/packages/binding-coap/src/coap-server.ts b/packages/binding-coap/src/coap-server.ts
index 8ef3c2ee8..e2acd028e 100644
--- a/packages/binding-coap/src/coap-server.ts
+++ b/packages/binding-coap/src/coap-server.ts
@@ -241,8 +241,8 @@ export default class CoapServer implements ProtocolServer {
         affordanceName: string,
         offeredMediaType: string,
         opValues: string | string[],
-        affordanceUriVariables,
-        thingUriVariables
+        affordanceUriVariables: PropertyElement["uriVariables"] = {},
+        thingUriVariables: PropertyElement["uriVariables"] = {}
     ): [string, TD.Form] {
         const href = this.createFormHref(
             base,
@@ -260,8 +260,8 @@ export default class CoapServer implements ProtocolServer {
         base: string,
         affordancePathSegment: string,
         affordanceName: string,
-        affordanceUriVariables,
-        thingUriVariables
+        affordanceUriVariables: PropertyElement["uriVariables"] = {},
+        thingUriVariables: PropertyElement["uriVariables"] = {}
     ) {
         const affordanceNamePattern = Helpers.updateInteractionNameWithUriVariablePattern(
             affordanceName,