diff --git a/lib/deref.js b/lib/deref.js
index c76a4b6..edfc3bc 100644
--- a/lib/deref.js
+++ b/lib/deref.js
@@ -188,7 +188,7 @@ module.exports = {
         let refResolvedSchema = this.resolveRefs(resolvedSchema, parameterSourceOption,
           components, schemaResolutionCache, resolveFor, stack, _.cloneDeep(seenRef));
 
-        if (refResolvedSchema.value !== ERR_TOO_MANY_LEVELS) {
+        if (refResolvedSchema && refResolvedSchema.value !== ERR_TOO_MANY_LEVELS) {
           schemaResolutionCache[refKey] = refResolvedSchema;
         }