diff --git a/flake.lock b/flake.lock
index 74cdaab..55670c9 100644
--- a/flake.lock
+++ b/flake.lock
@@ -4,8 +4,8 @@
       "inputs": {
         "artiq-comtools": "artiq-comtools",
         "mozilla-overlay": "mozilla-overlay",
-        "nixpkgs": "nixpkgs",
-        "sipyco": "sipyco",
+        "nixpkgs": "nixpkgs_2",
+        "sipyco": "sipyco_2",
         "src-migen": "src-migen",
         "src-misoc": "src-misoc",
         "src-pythonparser": "src-pythonparser"
@@ -26,14 +26,8 @@
     },
     "artiq-comtools": {
       "inputs": {
-        "nixpkgs": [
-          "artiq",
-          "nixpkgs"
-        ],
-        "sipyco": [
-          "artiq",
-          "sipyco"
-        ]
+        "nixpkgs": "nixpkgs",
+        "sipyco": "sipyco"
       },
       "locked": {
         "lastModified": 1644743100,
@@ -98,6 +92,22 @@
       }
     },
     "nixpkgs": {
+      "locked": {
+        "lastModified": 1646588256,
+        "narHash": "sha256-ZHljmNlt19nSm0Mz8fx6QEhddKUkU4hhwFmfNmGn+EY=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "2ebb6c1e5ae402ba35cca5eec58385e5f1adea04",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixos-21.11",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "nixpkgs_2": {
       "locked": {
         "lastModified": 1644472683,
         "narHash": "sha256-sP6iM4NksOYO6NFfTJ96cg+ClPnq6cdY30xKA1iYtyU=",
@@ -113,6 +123,22 @@
         "type": "github"
       }
     },
+    "nixpkgs_3": {
+      "locked": {
+        "lastModified": 1646588256,
+        "narHash": "sha256-ZHljmNlt19nSm0Mz8fx6QEhddKUkU4hhwFmfNmGn+EY=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "2ebb6c1e5ae402ba35cca5eec58385e5f1adea04",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixos-21.11",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
     "root": {
       "inputs": {
         "artiq": "artiq",
@@ -124,6 +150,7 @@
       "inputs": {
         "nixpkgs": [
           "artiq",
+          "artiq-comtools",
           "nixpkgs"
         ]
       },
@@ -141,6 +168,24 @@
         "type": "github"
       }
     },
+    "sipyco_2": {
+      "inputs": {
+        "nixpkgs": "nixpkgs_3"
+      },
+      "locked": {
+        "lastModified": 1644649772,
+        "narHash": "sha256-LE9L5bDSunCPEnuf5Ed8enTAXA2vkTSmjvqPX9ILO0Y=",
+        "owner": "m-labs",
+        "repo": "sipyco",
+        "rev": "8e4382352bc64bd01c9db35d9c9b0ef42b8b9d3b",
+        "type": "github"
+      },
+      "original": {
+        "owner": "m-labs",
+        "repo": "sipyco",
+        "type": "github"
+      }
+    },
     "src-migen": {
       "flake": false,
       "locked": {