diff --git a/blscurve/bls_batch_verifier.nim b/blscurve/bls_batch_verifier.nim
index 95dabcb..d44c6ed 100644
--- a/blscurve/bls_batch_verifier.nim
+++ b/blscurve/bls_batch_verifier.nim
@@ -54,31 +54,21 @@ type
 
     # Per-batch contexts for multithreaded batch verification
     batchContexts: seq[ContextMultiAggregateVerify[DST]]
-    when compileOption("threads"):
-      flows: seq[Flowvar[bool]]
 
 # Serial Batch Verifier
 # ----------------------------------------------------------------------
 
 func init*(T: type BatchedBLSVerifierCache): T =
   ## Initialise the cache for single-threaded usage
-  when compileOption("threads"):
-    BatchedBLSVerifierCache(
-      batchContexts: newSeq[ContextMultiAggregateVerify[DST]](1),
-      flows: @[]
-    )
-  else:
-    BatchedBLSVerifierCache(
-      batchContexts: newSeq[ContextMultiAggregateVerify[DST]](1),
-    )
-
+  BatchedBLSVerifierCache(
+    batchContexts: newSeq[ContextMultiAggregateVerify[DST]](1),
+  )
 
 when compileOption("threads"):
   func init*(T: type BatchedBLSVerifierCache, tp: Taskpool): T =
     ## Initialise the cache for multi-threaded usage
     BatchedBLSVerifierCache(
       batchContexts: newSeq[ContextMultiAggregateVerify[DST]](tp.numThreads),
-      flows: newSeq[Flowvar[bool]](tp.numThreads)
     )
 
 func batchVerifySerial*(
diff --git a/blscurve/eth2_keygen/hkdf.nim b/blscurve/eth2_keygen/hkdf.nim
index 2c476c0..fc6cda5 100644
--- a/blscurve/eth2_keygen/hkdf.nim
+++ b/blscurve/eth2_keygen/hkdf.nim
@@ -82,8 +82,8 @@
 
 import nimcrypto/hmac
 
-func hkdfExtract*[T;S,I: char|byte](ctx: var HMAC[T],
-                     prk: var MDigest[T.bits],
+func hkdfExtract*[T;M;S,I: char|byte](ctx: var HMAC[T],
+                     prk: var M, # MDigest[T.bits]
                      salt: openArray[S],
                      ikm: openArray[I],
                      append: static openArray[I]
@@ -108,6 +108,9 @@ func hkdfExtract*[T;S,I: char|byte](ctx: var HMAC[T],
   ## - ctx: a HMAC["cryptographic-hash"] context, for example HMAC[sha256].
 
   mixin init, update, finish
+
+  # TODO https://github.com/nim-lang/Nim/issues/22494
+  static: doAssert M.bits == T.bits
   ctx.init(salt)
   ctx.update(ikm)
   when append.len > 0:
@@ -116,8 +119,8 @@ func hkdfExtract*[T;S,I: char|byte](ctx: var HMAC[T],
 
   # ctx.clear() - TODO: very expensive
 
-func hkdfExpand*[T;I,A: char|byte](ctx: var HMAC[T],
-                    prk: MDigest[T.bits],
+func hkdfExpand*[T;M;I,A: char|byte](ctx: var HMAC[T],
+                    prk: M, # MDigest[T.bits]
                     info: openArray[I],
                     append: static openArray[A],
                     output: var openArray[byte]
@@ -141,6 +144,8 @@ func hkdfExpand*[T;I,A: char|byte](ctx: var HMAC[T],
   ## - ctx: a HMAC["cryptographic-hash"] context, for example HMAC[sha256].
   mixin init, update, finish
 
+  # TODO https://github.com/nim-lang/Nim/issues/22494
+  static: doAssert M.bits == T.bits
   const HashLen = T.bits div 8
 
   static: doAssert T.bits >= 0
diff --git a/blscurve/miracl/common.nim b/blscurve/miracl/common.nim
index b15f349..dae3fea 100644
--- a/blscurve/miracl/common.nim
+++ b/blscurve/miracl/common.nim
@@ -535,7 +535,7 @@ func fromBytes*(res: var BIG_384, a: openArray[byte]): bool =
   let length = if len(a) > MODBYTES_384: MODBYTES_384 else: len(a)
   for i in 0..<length:
     discard BIG_384_fshl(res, 8)
-    res[0] = res[0] + cast[Chunk](a[i])
+    res[0] = res[0] + Chunk(a[i])
   true
 
 func fromBytes*(res: var DBIG_384, a: openArray[byte]): bool =
@@ -547,7 +547,7 @@ func fromBytes*(res: var DBIG_384, a: openArray[byte]): bool =
   zeroMem(res.addr, sizeof(res))
   for rawByte in a:
     BIG_384_dshl(res, 8)
-    res[0] = res[0] + cast[Chunk](rawByte)
+    res[0] = res[0] + Chunk(rawByte)
   true
 
 func fromHex*(res: var BIG_384, a: string): bool {.inline.} =
@@ -556,7 +556,7 @@ func fromHex*(res: var BIG_384, a: string): bool {.inline.} =
   ## Returns ``true`` if conversion was successful.
   try:
     fromBytes(res, hexToSeqByte(a))
-  except ValueError, IndexError:
+  except ValueError:
     # TODO: change to exception-free
     # https://github.com/status-im/nim-blscurve/issues/57
     false
@@ -651,7 +651,7 @@ func fromHex*(res: var ECP2_BLS12381, a: string): bool {.inline.} =
   ## Returns ``true`` if conversion was successfull.
   try:
     fromBytes(res, hexToSeqByte(a))
-  except ValueError, IndexError:
+  except ValueError:
     # TODO: change to exception-free
     # https://github.com/status-im/nim-blscurve/issues/57
     false
@@ -737,7 +737,7 @@ func fromHex*(res: var ECP_BLS12381, a: string): bool {.inline.} =
   ## Returns ``true`` if conversion was successfull.
   try:
     fromBytes(res, hexToSeqByte(a))
-  except ValueError, IndexError:
+  except ValueError:
     # TODO: change to exception-free
     # https://github.com/status-im/nim-blscurve/issues/57
     false