diff --git a/.gitignore b/.gitignore
index a5a2eae..2b10673 100644
--- a/.gitignore
+++ b/.gitignore
@@ -22,3 +22,4 @@
 /Sereal-Encoder-4.018.tar.gz
 /Sereal-Encoder-4.019.tar.gz
 /Sereal-Encoder-4.020.tar.gz
+/Sereal-Encoder-4.021.tar.gz
diff --git a/perl-Sereal-Encoder.spec b/perl-Sereal-Encoder.spec
index 5b218eb..6ade5fc 100644
--- a/perl-Sereal-Encoder.spec
+++ b/perl-Sereal-Encoder.spec
@@ -6,7 +6,7 @@
 %endif
 
 Name:           perl-Sereal-Encoder
-Version:        4.020
+Version:        4.021
 Release:        1%{?dist}
 Summary:        Perl serialization into Sereal format
 # lib/Sereal/Encoder.pm:    GPL+ or Artistic
@@ -120,6 +120,11 @@ make test
 %{_mandir}/man3/Sereal::Encoder.3*
 
 %changelog
+* Fri Feb 18 2022 Paul Howarth <paul@city-fan.org> - 4.021-1
+- Update to 4.021
+  - Make it possible to upgrade with passing tests when using
+    Sereal::Decoder 4.019 on threaded debugging perls
+
 * Thu Feb 17 2022 Paul Howarth <paul@city-fan.org> - 4.020-1
 - Update to 4.020
   - Fix "panic: free from wrong pool" errors on threaded builds
diff --git a/sources b/sources
index a11a89a..d96f2d5 100644
--- a/sources
+++ b/sources
@@ -1 +1 @@
-SHA512 (Sereal-Encoder-4.020.tar.gz) = 33dcea20355ab6bad1c29871ab1abbea11761b9ab58f1760137ddac0adf2ad648850e9be9f79c7a2543b9ebbc48acfa53087759ca06e180344d6096ffc768945
+SHA512 (Sereal-Encoder-4.021.tar.gz) = db664326ffe536cbd424bdaaada72b25b60c70cfb029d4f04a792390b361fe0ea112973a287fa4b197d9d4ae0c915ac24f9aefc7c7c677c9db372a40ee4b5318