diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,8 @@
 # Changelog
 
+## [0.2.1.1] - 2021-02-27
+ * version bump of `constraints` dependency
+
 ## [0.2.1.0] - 2020-07-20
  * removeZeros is optional: Tensor addition and tensor contraction will not remove zero values afterwards in order to improve performance.
    Zero values have to be removed by explicitly applying removeZeros to a tensor.
diff --git a/README.md b/README.md
--- a/README.md
+++ b/README.md
@@ -1,4 +1,4 @@
-![Hackage-Deps](https://img.shields.io/hackage-deps/v/safe-tensor) [![Hackage](https://img.shields.io/hackage/v/safe-tensor)](https://hackage.haskell.org/package/safe-tensor) [![Build Status](https://travis-ci.org/nilsalex/safe-tensor.svg?branch=master)](https://travis-ci.org/nilsalex/safe-tensor)
+[![DOI](https://zenodo.org/badge/226436124.svg)](https://zenodo.org/badge/latestdoi/226436124) ![Hackage-Deps](https://img.shields.io/hackage-deps/v/safe-tensor) [![Hackage](https://img.shields.io/hackage/v/safe-tensor)](https://hackage.haskell.org/package/safe-tensor) [![Build Status](https://travis-ci.org/nilsalex/safe-tensor.svg?branch=master)](https://travis-ci.org/nilsalex/safe-tensor)
 # safe-tensor
 Dependently typed tensor algebra in Haskell. Useful for applications in field theory, e.g., carrying out calculations for https://doi.org/10.1103/PhysRevD.101.084025
 
diff --git a/safe-tensor.cabal b/safe-tensor.cabal
--- a/safe-tensor.cabal
+++ b/safe-tensor.cabal
@@ -4,10 +4,10 @@
 --
 -- see: https://github.com/sol/hpack
 --
--- hash: e0fcc8fb2efd3f5b62b7dd2ad65bca4521755f5226831bfe4553c23ab94904f6
+-- hash: 57f1d4d4204d9d53befa40b256d8a75bb2f3848e776bf1f784c3743a9f03e69f
 
 name:           safe-tensor
-version:        0.2.1.0
+version:        0.2.1.1
 synopsis:       Dependently typed tensor algebra
 description:    For an introduction to the library, see "Math.Tensor.Safe". For more information, see the README on GitHub at <https://github.com/nilsalex/safe-tensor#readme>
 category:       Math
@@ -51,7 +51,7 @@
   ghc-options: -Wall
   build-depends:
       base >=4.7 && <5
-    , constraints >=0.10 && <0.13
+    , constraints >=0.10 && <0.14
     , containers >=0.6 && <0.7
     , deepseq >=1.4 && <1.5
     , hmatrix >=0.20 && <0.21