diff --git a/.github/workflows/fluffy.yml b/.github/workflows/fluffy.yml
index 10fb8cbc7..b4e4e8efe 100644
--- a/.github/workflows/fluffy.yml
+++ b/.github/workflows/fluffy.yml
@@ -238,7 +238,9 @@ jobs:
 
       - name: Build Nim and Nimbus-eth1 dependencies
         run: |
-          make -j${ncpu} ARCH_OVERRIDE=${PLATFORM} CI_CACHE=NimBinaries update
+          # use CC to make sure Nim compiler and subsequent test
+          # using the same glibc version.
+          env CC=gcc make -j${ncpu} ARCH_OVERRIDE=${PLATFORM} CI_CACHE=NimBinaries update
 
       - name: Run fluffy tests (Windows)
         if: runner.os == 'Windows'
@@ -253,6 +255,9 @@ jobs:
       - name: Run fluffy tests (Linux)
         if: runner.os == 'Linux'
         run: |
+          gcc --version
+          ./env.sh nim -v
+          ldd --version
           export LD_LIBRARY_PATH="${LD_LIBRARY_PATH}:/usr/local/lib"
           DEFAULT_MAKE_FLAGS="-j${ncpu}"
           env CC=gcc make ${DEFAULT_MAKE_FLAGS} fluffy
diff --git a/fluffy/network/header/header_content.nim b/fluffy/network/header/header_content.nim
index f07c2b82f..324b04af5 100644
--- a/fluffy/network/header/header_content.nim
+++ b/fluffy/network/header/header_content.nim
@@ -25,6 +25,11 @@ type
 
   ContentType* = enum
     newBlockHeader = 0x00
+    # TODO: remove or fix this temporary 
+    # dummySelector per latest spec.
+    # This is temporary workaround
+    # to fool SSZ.isUnion    
+    dummySelector  = 0x01
 
   NewBlockHeaderKey* = object
     blockHash*: BlockHash
@@ -34,6 +39,8 @@ type
     case contentType*: ContentType
     of newBlockHeader:
       newBlockHeaderKey*: NewBlockHeaderKey
+    of dummySelector:
+      dummyField: uint64
 
 func encode*(contentKey: ContentKey): ByteList =
   ByteList.init(SSZ.encode(contentKey))
diff --git a/nimbus/graphql/ethapi.nim b/nimbus/graphql/ethapi.nim
index 5992235f4..f87eef183 100644
--- a/nimbus/graphql/ethapi.nim
+++ b/nimbus/graphql/ethapi.nim
@@ -70,6 +70,11 @@ type
     ethNode: EthereumNode
     txPool: TxPoolRef
 
+when (NimMajor, NimMinor, NimPatch) >= (1, 6, 0):
+  {.push hint[XCannotRaiseY]: off.}
+else:
+  {.push hint[XDeclaredButNotUsed]: off.}
+  
 proc toHash(n: Node): Hash256 =
   result.data = hexToByteArray[32](n.stringVal)
 
@@ -1333,3 +1338,5 @@ proc setupGraphqlHttpServer*(conf: NimbusConf,
     echo sres.error
     quit(QuitFailure)
   sres.get()
+
+{.pop.}
\ No newline at end of file
diff --git a/tests/replay/gunzip.nim b/tests/replay/gunzip.nim
index 2fbfca1d5..2da4921fc 100644
--- a/tests/replay/gunzip.nim
+++ b/tests/replay/gunzip.nim
@@ -52,12 +52,12 @@ proc explode(state: var GUnzip; data: openArray[char];
     outData = ""
     rc: ZError
 
-  state.mz.next_in  = cast[ptr cuchar](inBuf[0].addr)
+  state.mz.next_in  = cast[ptr uint8](inBuf[0].addr)
   state.mz.total_in = 0
   state.mz.avail_in = inBuf.len.cuint
 
   while not state.outDoneOK and 0 < state.mz.avail_in:
-    state.mz.next_out = cast[ptr cuchar](state.outBuf[0].addr)
+    state.mz.next_out = cast[ptr uint8](state.outBuf[0].addr)
     state.mz.avail_out = state.outBuf.len.cuint
     state.mz.total_out = 0
 
diff --git a/vendor/nim-chronicles b/vendor/nim-chronicles
index 972f25d6c..12f5621c9 160000
--- a/vendor/nim-chronicles
+++ b/vendor/nim-chronicles
@@ -1 +1 @@
-Subproject commit 972f25d6c3a324848728d2d05796209f1b9d120e
+Subproject commit 12f5621c90942bb531c8486bfa3711e88adbe015
diff --git a/vendor/nim-eth b/vendor/nim-eth
index 20d2d318f..4d55bfc9e 160000
--- a/vendor/nim-eth
+++ b/vendor/nim-eth
@@ -1 +1 @@
-Subproject commit 20d2d318f063d05a0a989b01be80e7560cda34c5
+Subproject commit 4d55bfc9e80b3af38cb179aaaad9331579e2b55b
diff --git a/vendor/nim-graphql b/vendor/nim-graphql
index 4ef25a2d0..de2f64ff7 160000
--- a/vendor/nim-graphql
+++ b/vendor/nim-graphql
@@ -1 +1 @@
-Subproject commit 4ef25a2d036da25c8e568b0bba426cc591fe7f19
+Subproject commit de2f64ff7bb039550f99323a17ac0d79b0f96a00
diff --git a/vendor/nim-json-rpc b/vendor/nim-json-rpc
index 64dbf122d..c0ecb4261 160000
--- a/vendor/nim-json-rpc
+++ b/vendor/nim-json-rpc
@@ -1 +1 @@
-Subproject commit 64dbf122d7457ceabdacfb26131e929f26f15581
+Subproject commit c0ecb426131ebc2c3d11c085d749f55884f6fea6
diff --git a/vendor/nim-serialization b/vendor/nim-serialization
index 493d18b82..257e2e02e 160000
--- a/vendor/nim-serialization
+++ b/vendor/nim-serialization
@@ -1 +1 @@
-Subproject commit 493d18b8292fc03aa4f835fd825dea1183f97466
+Subproject commit 257e2e02ebe2efbe86beb05c62a739fc9c3d10e7
diff --git a/vendor/nim-ssz-serialization b/vendor/nim-ssz-serialization
index 639758dbd..3a6c350f5 160000
--- a/vendor/nim-ssz-serialization
+++ b/vendor/nim-ssz-serialization
@@ -1 +1 @@
-Subproject commit 639758dbd9a5f3e75a15449ddf80d6fd1cfa585e
+Subproject commit 3a6c350f515829af327a4238ba60a384f7a02520
diff --git a/vendor/nim-toml-serialization b/vendor/nim-toml-serialization
index 4879c8893..2c46429b8 160000
--- a/vendor/nim-toml-serialization
+++ b/vendor/nim-toml-serialization
@@ -1 +1 @@
-Subproject commit 4879c8893c1d89495f088b9e2488417935d235d4
+Subproject commit 2c46429b822347aa2db04e04671988de734d2b78
diff --git a/vendor/nim-websock b/vendor/nim-websock
index 2424f2b21..fea05cde8 160000
--- a/vendor/nim-websock
+++ b/vendor/nim-websock
@@ -1 +1 @@
-Subproject commit 2424f2b215c0546f97d8b147e21544521c7545b0
+Subproject commit fea05cde8b123b38d1a0a8524b77efbc84daa848
diff --git a/vendor/nim-zlib b/vendor/nim-zlib
index 74cdeb54b..cd3ef7766 160000
--- a/vendor/nim-zlib
+++ b/vendor/nim-zlib
@@ -1 +1 @@
-Subproject commit 74cdeb54b21bededb5a515d36f608bc1850555a2
+Subproject commit cd3ef7766b803fc41174b9b0757a748df189db72
diff --git a/vendor/nimbus-build-system b/vendor/nimbus-build-system
index 72d51e4c3..ba832c296 160000
--- a/vendor/nimbus-build-system
+++ b/vendor/nimbus-build-system
@@ -1 +1 @@
-Subproject commit 72d51e4c320fbdbdee4d6a28c2a621cda44b7143
+Subproject commit ba832c296eb575b84190ae2a43a842019cda37b2