diff --git a/lock.json b/lock.json
index ecfe8ed..aebfdff 100644
--- a/lock.json
+++ b/lock.json
@@ -1,5 +1,17 @@
 {
   "depends": [
+    {
+      "method": "fetchzip",
+      "packages": [
+        "bigints"
+      ],
+      "path": "/nix/store/jvrm392g8adfsgf36prgwkbyd7vh5jsw-source",
+      "ref": "20231006",
+      "rev": "86ea14d31eea9275e1408ca34e6bfe9c99989a96",
+      "sha256": "15pcpmnk1bnw3k8769rjzcpg00nahyrypwbxs88jnwr4aczp99j4",
+      "srcDir": "src",
+      "url": "https://github.com/ehmry/nim-bigints/archive/86ea14d31eea9275e1408ca34e6bfe9c99989a96.tar.gz"
+    },
     {
       "method": "fetchzip",
       "packages": [
diff --git a/src/syndicate/patterns.nim b/src/syndicate/patterns.nim
index 4e0ad64..a8b6c65 100644
--- a/src/syndicate/patterns.nim
+++ b/src/syndicate/patterns.nim
@@ -75,8 +75,8 @@ proc grab*[T](pr: Preserve[T]): Pattern =
     AnyAtom(orKind: AnyAtomKind.`float`, float: pr.float).toPattern
   of pkDouble:
     AnyAtom(orKind: AnyAtomKind.`double`, double: pr.double).toPattern
-  of pkSignedInteger:
-    AnyAtom(orKind: AnyAtomKind.`int`, int: pr.int).toPattern
+  of pkRegister:
+    AnyAtom(orKind: AnyAtomKind.`int`, int: pr.register).toPattern
   of pkString:
     AnyAtom(orKind: AnyAtomKind.`string`, string: pr.string).toPattern
   of pkByteString:
@@ -101,6 +101,8 @@ proc grab*[T](pr: Preserve[T]): Pattern =
   of pkEmbedded:
     # TODO: can patterns be constructed over embedded literals?
     drop()
+  else:
+    raise newException(ValueError, "cannot generate a pattern for unhandled Value type")
 
 proc grab*[T](val: T): Pattern =
   ## Construct a `Pattern` from value of type `T`.