diff --git a/Manifest.txt b/Manifest.txt
index da43167d..99826ef4 100644
--- a/Manifest.txt
+++ b/Manifest.txt
@@ -128,6 +128,7 @@ test/fixtures/binary-content-transfer-encoding-2.eml
 test/fixtures/blank-header-fields.eml
 test/fixtures/contacts.txt
 test/fixtures/embedded-message.eml
+test/fixtures/invalid-date.eml
 test/fixtures/mailing-list-header.eml
 test/fixtures/malicious-attachment-names.eml
 test/fixtures/missing-from-to.eml
diff --git a/lib/sup/message.rb b/lib/sup/message.rb
index 0a0bcc6e..3354507c 100644
--- a/lib/sup/message.rb
+++ b/lib/sup/message.rb
@@ -103,7 +103,7 @@ def parse_header encoded_header
     when Time
       date
     when String
-      Time.parse date rescue nil
+      Time.rfc2822 date rescue nil
     end
     @date = location.fallback_date if @date.nil?
     @date = Time.utc 1970, 1, 1 if @date.nil?
diff --git a/test/dummy_source.rb b/test/dummy_source.rb
index d8515313..1e2492a0 100644
--- a/test/dummy_source.rb
+++ b/test/dummy_source.rb
@@ -10,10 +10,12 @@ module Redwood
 class DummySource < Source
 
   attr_accessor :messages
+  attr_writer :fallback_date
 
   def initialize uri, last_date=nil, usual=true, archived=false, id=nil, labels=[]
     super uri, usual, archived, id
     @messages = nil
+    @fallback_date = Time.utc 2001, 2, 3, 4, 56, 57
   end
 
   def start_offset
@@ -61,7 +63,7 @@ def each_raw_message_line id
   end
 
   def fallback_date_for_message id
-    Time.utc 2001, 2, 3, 4, 56, 57
+    @fallback_date
   end
 end
 
diff --git a/test/fixtures/invalid-date.eml b/test/fixtures/invalid-date.eml
new file mode 100644
index 00000000..0ab49962
--- /dev/null
+++ b/test/fixtures/invalid-date.eml
@@ -0,0 +1,8 @@
+To: person@example.invalid
+Subject: pre-RFC2822 Date header
+Content-type: text/plain
+From: anotherperson@example.invalid
+Message-Id: <6965470922807932796@example.invalid>
+Date: ons, 26 maj 1999 11:00:34 +0200 (CEST)
+
+A message body.
diff --git a/test/test_message.rb b/test/test_message.rb
index d009a01e..3a8a1f48 100644
--- a/test/test_message.rb
+++ b/test/test_message.rb
@@ -359,6 +359,19 @@ def test_malicious_attachment_names
     fn = chunks[3].safe_filename
     assert_equal(fn, File.basename(fn))
   end
+
+  def test_invalid_date_header
+    fallback_date = Time.utc 2024, 5, 12, 15, 5, 56
+    source = DummySource.new("sup-test://test_invalid_date_header")
+    source.messages = [ fixture_path("invalid-date.eml") ]
+    source.fallback_date = fallback_date
+
+    sup_message = Message.build_from_source(source, 0)
+    sup_message.load_from_source!
+
+    assert_equal(fallback_date, sup_message.date)
+  end
+
   # TODO: test different error cases, malformed messages etc.
 
   # TODO: test different quoting styles, see that they are all divided