diff --git a/lib/shared-method.js b/lib/shared-method.js
index 5b469e64..6536d30c 100644
--- a/lib/shared-method.js
+++ b/lib/shared-method.js
@@ -398,8 +398,15 @@ function convertValueToTargetType(argName, value, targetType) {
   switch (targetType) {
     case 'string':
       return String(value).valueOf();
-    case 'date':
+    case 'date': {
+
+      // could be a timestamp as string
+      if (!isNaN(value) && typeof value == 'string') {
+        value = Number(value).valueOf();
+      }
+
       return new Date(value);
+    }
     case 'number':
       return Number(value).valueOf();
     case 'boolean':