diff --git a/lib/err-helpers.js b/lib/err-helpers.js
index d00c201..1164a33 100644
--- a/lib/err-helpers.js
+++ b/lib/err-helpers.js
@@ -12,7 +12,7 @@
 const getErrorCause = (err) => {
   if (!err) return
 
-  const cause = evaluateCause(err.cause)
+  const cause = evaluateCause(err)
 
   return cause instanceof Error
     ? cause
@@ -20,14 +20,14 @@ const getErrorCause = (err) => {
 }
 
 /**
- * @param {unknown|(()=>err)} cause
+ * @param {Error|{ cause?: unknown|(()=>err)}} err
  * @returns {Error|undefined}
  */
-const evaluateCause = (cause) => {
+const evaluateCause = (err) => {
   // VError / NError style causes are functions
-  return typeof cause === 'function'
-    ? cause()
-    : cause
+  return typeof err.cause === 'function'
+    ? err.cause()
+    : err.cause
 }
 
 /**
diff --git a/lib/err.js b/lib/err.js
index fd63e23..665bba2 100644
--- a/lib/err.js
+++ b/lib/err.js
@@ -66,7 +66,7 @@ function errSerializer (err) {
   }
 
   if (err.cause) {
-    const cause = evaluateCause(err.cause)
+    const cause = evaluateCause(err)
     _err.cause = errSerializer(cause)
   }