diff --git a/src/Exceptions/InvalidDate.php b/src/Exceptions/InvalidDate.php
index e76b624..da1f626 100644
--- a/src/Exceptions/InvalidDate.php
+++ b/src/Exceptions/InvalidDate.php
@@ -6,6 +6,11 @@
 
 class InvalidDate extends InvalidArgumentException
 {
+    public static function cannotBeNull(string $parameter): InvalidDate
+    {
+        return new static("{$parameter} cannot be null");
+    }
+
     public static function forFormat(string $date, ?string $format): InvalidDate
     {
         $message = "Could not construct a date from `{$date}`";
diff --git a/src/Period.php b/src/Period.php
index 295e856..c4ea954 100644
--- a/src/Period.php
+++ b/src/Period.php
@@ -36,6 +36,14 @@ public function __construct(DateTimeImmutable $start, DateTimeImmutable $end)
      */
     public static function make($start, $end, string $format = null): Period
     {
+        if ($start === null) {
+            throw InvalidDate::cannotBeNull('Start date');
+        }
+
+        if ($end === null) {
+            throw InvalidDate::cannotBeNull('Endß date');
+        }
+
         return new static(
             self::resolveDate($start, $format),
             self::resolveDate($end, $format)