diff --git a/pkgs/common-updater/scripts/update-source-version b/pkgs/common-updater/scripts/update-source-version
index 12a63fa92605..75ad6e7a5cf5 100755
--- a/pkgs/common-updater/scripts/update-source-version
+++ b/pkgs/common-updater/scripts/update-source-version
@@ -237,9 +237,13 @@ fi
 if [[ -z "$newHash" ]]; then
     nix-build $systemArg --no-out-link -A "$attr.$sourceKey" 2>"$attr.fetchlog" >/dev/null || true
     # FIXME: use nix-build --hash here once https://github.com/NixOS/nix/issues/1172 is fixed
-    newHash=$(sed '1,/hash mismatch in fixed-output derivation/d' "$attr.fetchlog" | grep --perl-regexp --only-matching 'got: +.+[:-]\K.+')
+    newHash=$(
+        sed '1,/hash mismatch in fixed-output derivation/d' "$attr.fetchlog" \
+        | grep --perl-regexp --only-matching 'got: +.+[:-]\K.+' \
+        || true # handled below
+    )
 
-    if [[ -n "$sri" ]]; then
+    if [[ -n "$newHash" && -n "$sri" ]]; then
         # nix-build preserves the hashing scheme so we can just convert the result to SRI using the old type
         newHash="$(nix --extra-experimental-features nix-command hash to-sri --type "$oldHashAlgo" "$newHash" 2>/dev/null \
             || nix to-sri --type "$oldHashAlgo" "$newHash" 2>/dev/null)" \
diff --git a/pkgs/desktops/gnome/update.nix b/pkgs/desktops/gnome/update.nix
index f5db71174ad8..e945e005d48d 100644
--- a/pkgs/desktops/gnome/update.nix
+++ b/pkgs/desktops/gnome/update.nix
@@ -12,7 +12,13 @@ let
       minorAvailable = builtins.length versionComponents > 1 && builtins.match "[0-9]+" minorVersion != null;
       nextMinor = builtins.fromJSON minorVersion + 1;
       upperBound = "${lib.versions.major packageVersion}.${builtins.toString nextMinor}";
-    in lib.optionals (freeze && minorAvailable) [ upperBound ];
+    in
+    if builtins.isBool freeze then
+      lib.optionals (freeze && minorAvailable) [ upperBound ]
+    else if builtins.isString freeze then
+      [ freeze ]
+    else
+      throw "“freeze” argument needs to be either a boolean, or a version string.";
   updateScript = writeScript "gnome-update-script" ''
     #!${bash}/bin/bash
     set -o errexit
diff --git a/pkgs/development/libraries/libgweather/default.nix b/pkgs/development/libraries/libgweather/default.nix
index cae2095f8ebd..bc9a04685840 100644
--- a/pkgs/development/libraries/libgweather/default.nix
+++ b/pkgs/development/libraries/libgweather/default.nix
@@ -74,6 +74,8 @@ stdenv.mkDerivation rec {
     updateScript = gnome.updateScript {
       packageName = pname;
       versionPolicy = "odd-unstable";
+      # Version 40.alpha preceded version 4.0.
+      freeze = "40.alpha";
     };
   };