diff --git a/lib/dao.js b/lib/dao.js
index 9527d17d..55846e7e 100644
--- a/lib/dao.js
+++ b/lib/dao.js
@@ -768,17 +768,28 @@ DataAccessObject._normalize = function (filter) {
 };
 
 function DateType(arg) {
-  return new Date(arg);
+  var d = new Date(arg);
+  if (isNaN(d.getTime())) {
+    throw new Error('Invalid date: ' + arg);
+  }
+  return d;
 }
 
-function BooleanType(val) {
-  if (val === 'true') {
-    return true;
-  } else if (val === 'false') {
-    return false;
-  } else {
-    return Boolean(val);
+function BooleanType(arg) {
+  if (typeof arg === 'string') {
+    switch (arg) {
+      case 'true':
+      case '1':
+        return true;
+      case 'false':
+      case '0':
+        return false;
+    }
   }
+  if (arg == null) {
+    return null;
+  }
+  return Boolean(arg);
 }
 
 function NumberType(val) {