diff --git a/.github/workflows/nix-action-8.19.yml b/.github/workflows/nix-action-8.19.yml
index 6319812..7062a6b 100644
--- a/.github/workflows/nix-action-8.19.yml
+++ b/.github/workflows/nix-action-8.19.yml
@@ -3621,6 +3621,7 @@ jobs:
     - coq
     - mathcomp-analysis
     - mathcomp-algebra-tactics
+    - interval
     runs-on: ubuntu-latest
     steps:
     - name: Determine which commit to initially checkout
@@ -3674,6 +3675,10 @@ jobs:
       name: 'Building/fetching previous CI target: mathcomp-algebra-tactics'
       run: NIXPKGS_ALLOW_UNFREE=1 nix-build --no-out-link --argstr bundle "8.19" --argstr
         job "mathcomp-algebra-tactics"
+    - if: steps.stepCheck.outputs.status == 'built'
+      name: 'Building/fetching previous CI target: interval'
+      run: NIXPKGS_ALLOW_UNFREE=1 nix-build --no-out-link --argstr bundle "8.19" --argstr
+        job "interval"
     - if: steps.stepCheck.outputs.status == 'built'
       name: Building/fetching current CI target
       run: NIXPKGS_ALLOW_UNFREE=1 nix-build --no-out-link --argstr bundle "8.19" --argstr
diff --git a/.nix/nixpkgs.nix b/.nix/nixpkgs.nix
index 1626704..f6b6074 100644
--- a/.nix/nixpkgs.nix
+++ b/.nix/nixpkgs.nix
@@ -1,4 +1,4 @@
 fetchTarball {
-    url = https://github.com/NixOS/nixpkgs/archive/a2f49d26d32eeaf57d3873d508c746d4e791d804.tar.gz;
-    sha256 = "1888sil7pf8s6yr2kya4as42ar11aggsgin2is94a1vqz64zq03d";
-  }
+         url = https://github.com/vbgl/nixpkgs/archive/247d897cd075c897cff9915a51eb2c194d9fa32b.tar.gz;
+         sha256 = "12q2lzfz5aqqh3pdxh394mrvinip4c8qh72p369qs35sz4fd5m41";
+       }