diff --git a/beacon_chain/winservice.nim b/beacon_chain/winservice.nim
index acfcf042a..e5a131f9e 100644
--- a/beacon_chain/winservice.nim
+++ b/beacon_chain/winservice.nim
@@ -47,6 +47,7 @@ when defined(windows):
     SERVICE_CONTROL_INTERROGATE = 4
     SERVICE_ACCEPT_STOP = 1
     ERROR_INVALID_PARAMETER = 87
+    ERROR_INVALID_ACCESS = 12
     ERROR_BAD_CONFIGURATION = 1610
     NO_ERROR = 0
 
@@ -155,11 +156,15 @@ when defined(windows):
         reportServiceStatus(SERVICE_STOPPED, ERROR_BAD_CONFIGURATION, 0)
         quit QuitFailure
 
-      argEntryPoint(config)
-
-      info "Service thread stopped"
-      reportServiceStatus(SERVICE_STOPPED, NO_ERROR, 0)
+      try:
+        argEntryPoint(config)
+        info "Service thread stopped"
         # we have to report back when we stopped!
+        reportServiceStatus(SERVICE_STOPPED, NO_ERROR, 0)
+      except CatchableError:
+        info "Service thread crashed"
+        # we have to report back when we stopped!
+        reportServiceStatus(SERVICE_STOPPED, ERROR_INVALID_ACCESS, 0)
 
     let serviceName = newWideCString(argServiceName)
 
diff --git a/nix/checksums.nix b/nix/checksums.nix
index 2c8f2c54c..d79345d24 100644
--- a/nix/checksums.nix
+++ b/nix/checksums.nix
@@ -8,5 +8,5 @@ in pkgs.fetchFromGitHub {
   repo = "checksums";
   rev = tools.findKeyValue "^ +ChecksumsStableCommit = \"([a-f0-9]+)\"$" sourceFile;
   # WARNING: Requires manual updates when Nim compiler version changes.
-  hash = "sha256-RB2IXs2xcfYHhV9d7l1mtHW51mtsrqrYRapSoTikvHw=";
+  hash = "sha256-Bm5iJoT2kAvcTexiLMFBa9oU5gf7d4rWjo3OiN7obWQ=";
 }
diff --git a/nix/default.nix b/nix/default.nix
index a444329eb..a84a538e2 100644
--- a/nix/default.nix
+++ b/nix/default.nix
@@ -59,10 +59,13 @@ in stdenv.mkDerivation rec {
     pushd vendor/nimbus-build-system/vendor/Nim
     mkdir dist
     cp -r ${callPackage ./nimble.nix {}}    dist/nimble
-    cp -r ${callPackage ./checksums.nix {}} dist/checksums
+    chmod 777 -R dist/nimble
+    mkdir -p dist/nimble/dist
+    cp -r ${callPackage ./sat.nix {}}       dist/nimble/dist/sat
+    cp -r ${callPackage ./checksums.nix {}} dist/checksums  # need both
+    cp -r ${callPackage ./checksums.nix {}} dist/nimble/dist/checksums
     cp -r ${callPackage ./csources.nix {}}  csources_v2
     chmod 777 -R dist/nimble csources_v2
-    sed -i 's/isGitRepo(destDir)/false/' tools/deps.nim
     popd
   '';
 
diff --git a/nix/nimble.nix b/nix/nimble.nix
index 8eec4b414..5343aaa81 100644
--- a/nix/nimble.nix
+++ b/nix/nimble.nix
@@ -8,5 +8,5 @@ in pkgs.fetchFromGitHub {
   repo = "nimble";
   rev = tools.findKeyValue "^ +NimbleStableCommit = \"([a-f0-9]+)\".+" sourceFile;
   # WARNING: Requires manual updates when Nim compiler version changes.
-  hash = "sha256-qJcDKnc+9iUvYrZCMUbBbws+Qqa9vmWyCRsvOUEmq8U=";
+  hash = "sha256-sa0irAZjQRZLduEMBPf7sHlY1FigBJTR/vIH4ihii/w=";
 }
diff --git a/nix/sat.nix b/nix/sat.nix
new file mode 100644
index 000000000..ca6403f68
--- /dev/null
+++ b/nix/sat.nix
@@ -0,0 +1,12 @@
+{ pkgs ? import <nixpkgs> { } }:
+
+let
+  tools = pkgs.callPackage ./tools.nix {};
+  sourceFile = ../vendor/nimbus-build-system/vendor/Nim/koch.nim;
+in pkgs.fetchFromGitHub {
+  owner = "nim-lang";
+  repo = "sat";
+  rev = tools.findKeyValue "^ +SatStableCommit = \"([a-f0-9]+)\"$" sourceFile;
+  # WARNING: Requires manual updates when Nim compiler version changes.
+  hash = "sha256-JFrrSV+mehG0gP7NiQ8hYthL0cjh44HNbXfuxQNhq7c=";
+}
diff --git a/nix/shell.nix b/nix/shell.nix
index 5cacda064..8b5fe3c51 100644
--- a/nix/shell.nix
+++ b/nix/shell.nix
@@ -22,6 +22,7 @@ in pkgs.mkShell {
     lsof    # for killing processes by port
     killall # for killing processes manually
     curl    # for working with the node APIs
+    jq      # for parsing beacon API for LC start
     openjdk # for running web3signer
 
     mkdocs-python
diff --git a/vendor/nimbus-build-system b/vendor/nimbus-build-system
index 741274439..c3241765e 160000
--- a/vendor/nimbus-build-system
+++ b/vendor/nimbus-build-system
@@ -1 +1 @@
-Subproject commit 741274439ce72162ab3c740e7c0ef624d32725f9
+Subproject commit c3241765e3896a06ed372dddc9dd6e3c36fae8f6