diff --git a/index.js b/index.js
index 088efe3..188497e 100644
--- a/index.js
+++ b/index.js
@@ -578,12 +578,14 @@ function Date (year, month, day, hour, minute, second, millisecond, timezone) {
     case 7:
       d = new _Date(year, month, day, hour, minute, second, millisecond); break;
   }
-  if (timezone) {
-    // set time given timezone relative to the currently set local time
-    // (changing the internal "time" milliseconds value unless ms specified)
-    d.setTimezone(timezone, !(argc == 1 && typeof year === 'number'));
-  } else {
-    d.setTimezone(exports.currentTimezone);
+  if (!isNaN(d)) {
+    if (timezone) {
+      // set time given timezone relative to the currently set local time
+      // (changing the internal "time" milliseconds value unless ms specified)
+      d.setTimezone(timezone, !(argc == 1 && typeof year === 'number'));
+    } else {
+      d.setTimezone(exports.currentTimezone);
+    }
   }
   return d;
 }