diff --git a/gnu/packages/gnuzilla.scm b/gnu/packages/gnuzilla.scm
index 61dac7df57..365626a62a 100644
--- a/gnu/packages/gnuzilla.scm
+++ b/gnu/packages/gnuzilla.scm
@@ -550,8 +550,8 @@ (define* (computed-origin-method gexp-promise hash-algo hash
                       #:system system
                       #:guile-for-build guile)))
 
-(define %icecat-version "78.3.0-guix0-preview1")
-(define %icecat-build-id "20200921000000") ;must be of the form YYYYMMDDhhmmss
+(define %icecat-version "78.3.1-guix0-preview1")
+(define %icecat-build-id "20200926000000") ;must be of the form YYYYMMDDhhmmss
 
 ;; 'icecat-source' is a "computed" origin that generates an IceCat tarball
 ;; from the corresponding upstream Firefox ESR tarball, using the 'makeicecat'
@@ -573,11 +573,11 @@ (define icecat-source
                   "firefox-" upstream-firefox-version ".source.tar.xz"))
             (sha256
              (base32
-              "1xvvizv84v4w3mq56vphccpwagga1i9lgbvj1l0cs763sqi3w9w5"))))
+              "1savwk91vhvg096w289xwpjvqbbd2ibfad90081hirlzd1kpvljz"))))
 
-         (upstream-icecat-base-version "78.3.0") ; maybe older than base-version
+         (upstream-icecat-base-version "78.3.1") ; maybe older than base-version
          ;;(gnuzilla-commit (string-append "v" upstream-icecat-base-version))
-         (gnuzilla-commit "df6b2146f13fc90ad3c11136115ada077383ee2a")
+         (gnuzilla-commit "cd2af837fce69145effef83def6993d244887b03")
          (gnuzilla-source
           (origin
             (method git-fetch)
@@ -589,7 +589,7 @@ (define icecat-source
                                       (string-take gnuzilla-commit 8)))
             (sha256
              (base32
-              "0nmkb2d6jpfnx081w8gdbs264j9rg9whq2gna9d4wazdpds1pyfr"))))
+              "0266gp8vs4avlfdnr8dj7b47msxv1vkd0xpnifp04v4scvgj0yaj"))))
 
          (gnuzilla-fixes-patch
           (local-file (search-patch "icecat-use-older-reveal-hidden-html.patch")))
diff --git a/gnu/packages/patches/icecat-makeicecat.patch b/gnu/packages/patches/icecat-makeicecat.patch
index 8e1263085a..c90950d5ef 100644
--- a/gnu/packages/patches/icecat-makeicecat.patch
+++ b/gnu/packages/patches/icecat-makeicecat.patch
@@ -25,7 +25,7 @@ index 8be2362..48716f2 100755
 -wget -N https://ftp.mozilla.org/pub/mozilla.org/firefox/releases/${FFVERSION}esr/source/firefox-${FFVERSION}esr.source.tar.xz.asc
 -gpg --recv-keys --keyserver keyserver.ubuntu.com 14F26682D0916CDD81E37B6D61B7B526D98F0353
 -gpg --verify firefox-${FFVERSION}esr.source.tar.xz.asc
--echo -n 85273e22d6c31ccd000d72af47530cea3dc52f63f06e53701d9c6c82f68f7bf7 firefox-${FFVERSION}esr.source.tar.xz |sha256sum -c -
+-echo -n 5fd27d67689fe60803022035e556146d2dbce5e53d21c14d026fc31dd2e45be9 firefox-${FFVERSION}esr.source.tar.xz |sha256sum -c -
 -
 -echo Extracting Firefox tarball
 -tar -xf firefox-${FFVERSION}esr.source.tar.xz
@@ -37,7 +37,7 @@ index 8be2362..48716f2 100755
 +# wget -N https://ftp.mozilla.org/pub/mozilla.org/firefox/releases/${FFVERSION}esr/source/firefox-${FFVERSION}esr.source.tar.xz.asc
 +# gpg --recv-keys --keyserver keyserver.ubuntu.com 14F26682D0916CDD81E37B6D61B7B526D98F0353
 +# gpg --verify firefox-${FFVERSION}esr.source.tar.xz.asc
-+# echo -n 85273e22d6c31ccd000d72af47530cea3dc52f63f06e53701d9c6c82f68f7bf7 firefox-${FFVERSION}esr.source.tar.xz |sha256sum -c -
++# echo -n 5fd27d67689fe60803022035e556146d2dbce5e53d21c14d026fc31dd2e45be9 firefox-${FFVERSION}esr.source.tar.xz |sha256sum -c -
 +# 
 +# echo Extracting Firefox tarball
 +# tar -xf firefox-${FFVERSION}esr.source.tar.xz