diff --git a/gnu/packages/cran.scm b/gnu/packages/cran.scm
index a244fed0eb..5c825646c1 100644
--- a/gnu/packages/cran.scm
+++ b/gnu/packages/cran.scm
@@ -21345,14 +21345,14 @@ (define-public r-rstan
 (define-public r-rstanarm
   (package
     (name "r-rstanarm")
-    (version "2.19.3")
+    (version "2.21.1")
     (source
      (origin
        (method url-fetch)
        (uri (cran-uri "rstanarm" version))
        (sha256
         (base32
-         "0gxjq8bdlvdd8kn3dhp12xlymdab036r7n12lzmd3xlkl4cnxq3s"))))
+         "04ggzak3f7jaxza3dxyrmxp5b48qcgyspy22ykbhr03g4hzp7jk8"))))
     (properties `((upstream-name . "rstanarm")))
     (build-system r-build-system)
     (inputs
@@ -21374,6 +21374,8 @@ (define-public r-rstanarm
        ("r-shinystan" ,r-shinystan)
        ("r-stanheaders" ,r-stanheaders)
        ("r-survival" ,r-survival)))
+    (native-inputs
+     `(("r-knitr" ,r-knitr)))
     (home-page "https://mc-stan.org/rstanarm/")
     (synopsis "Bayesian applied regression modeling via Stan")
     (description