diff --git a/codex.nimble b/codex.nimble
index d3e017aa..e3348d80 100644
--- a/codex.nimble
+++ b/codex.nimble
@@ -13,7 +13,7 @@ requires "nim >= 1.2.0",
          "chronicles >= 0.7.2",
          "chronos >= 2.5.2",
          "confutils",
-         "ethers >= 0.1.6 & < 0.2.0",
+         "ethers >= 0.1.7 & < 0.2.0",
          "libbacktrace",
          "libp2p",
          "metrics",
diff --git a/codex/contracts/clock.nim b/codex/contracts/clock.nim
index 718c7ce4..dd17986f 100644
--- a/codex/contracts/clock.nim
+++ b/codex/contracts/clock.nim
@@ -21,13 +21,13 @@ proc start*(clock: OnChainClock) {.async.} =
     return
   clock.started = true
 
-  proc onBlock(blck: Block) {.gcsafe, upraises:[].} =
+  proc onBlock(blck: Block) {.async, upraises:[].} =
     let blockTime = blck.timestamp.truncate(int64)
     let computerTime = getTime().toUnix
     clock.offset = blockTime - computerTime
 
   if latestBlock =? (await clock.provider.getBlock(BlockTag.latest)):
-    onBlock(latestBlock)
+    await onBlock(latestBlock)
 
   clock.subscription = await clock.provider.subscribe(onBlock)
 
diff --git a/vendor/nim-ethers b/vendor/nim-ethers
index 0549800a..270d358b 160000
--- a/vendor/nim-ethers
+++ b/vendor/nim-ethers
@@ -1 +1 @@
-Subproject commit 0549800af6551525cbca2998ce51d0a66f25a3ec
+Subproject commit 270d358b869d02a4c625dde971f799db336670fb