diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index b46ec1e..e7ab7dc 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -8,6 +8,7 @@ jobs:
       max-parallel: 20
       matrix:
         test_lang: [c]
+        branch: [version-1-6]
         target:
           - os: linux
             cpu: amd64
@@ -17,24 +18,22 @@ jobs:
             cpu: amd64
           - os: windows
             cpu: amd64
-          - os: windows
-            cpu: i386
         include:
           - target:
               os: linux
-            builder: ubuntu-18.04
+            builder: ubuntu-20.04
           - target:
               os: macos
-            builder: macos-10.15
+            builder: macos-11
           - target:
               os: windows
-            builder: windows-2019
+            builder: windows-latest
 
-    name: '${{ matrix.target.os }}-${{ matrix.target.cpu }}-${{ matrix.test_lang }}'
+    name: '${{ matrix.target.os }}-${{ matrix.target.cpu }}-${{ matrix.test_lang }}-(Nim ${{ matrix.branch }})'
     runs-on: ${{ matrix.builder }}
     steps:
       - name: Checkout nim-ethash
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
         with:
           path: nim-ethash
           submodules: false
@@ -62,7 +61,7 @@ jobs:
       - name: Restore MinGW-W64 (Windows) from cache
         if: runner.os == 'Windows'
         id: windows-mingw-cache
-        uses: actions/cache@v2
+        uses: actions/cache@v3
         with:
           path: external/mingw-${{ matrix.target.cpu }}
           key: 'mingw-${{ matrix.target.cpu }}'
@@ -70,7 +69,7 @@ jobs:
       - name: Restore Nim DLLs dependencies (Windows) from cache
         if: runner.os == 'Windows'
         id: windows-dlls-cache
-        uses: actions/cache@v2
+        uses: actions/cache@v3
         with:
           path: external/dlls-${{ matrix.target.cpu }}
           key: 'dlls-${{ matrix.target.cpu }}'
@@ -120,11 +119,11 @@ jobs:
             git ls-remote "https://github.com/$1" "${2:-HEAD}" | cut -f 1
           }
           nbsHash=$(getHash status-im/nimbus-build-system)
-          echo "::set-output name=nimbus_build_system::$nbsHash"
+          echo "nimbus_build_system=$nbsHash" >> $GITHUB_OUTPUT
 
       - name: Restore prebuilt Nim from cache
         id: nim-cache
-        uses: actions/cache@v2
+        uses: actions/cache@v3
         with:
           path: NimBinaries
           key: '${{ matrix.test_lang }}-${{ matrix.target.os }}-${{ matrix.target.cpu }}-${{ steps.versions.outputs.nimbus_build_system }}'
@@ -143,7 +142,9 @@ jobs:
           else
             MAKE_CMD="make"
           fi
-          env MAKE="$MAKE_CMD -j2" ARCH_OVERRIDE=$PLATFORM CC=gcc bash build_nim.sh nim csources dist/nimble NimBinaries
+          env MAKE="$MAKE_CMD -j2" ARCH_OVERRIDE=$PLATFORM NIM_COMMIT=${{ matrix.branch }} \
+            QUICK_AND_DIRTY_COMPILER=1 QUICK_AND_DIRTY_NIMBLE=1 CC=gcc \
+            bash build_nim.sh nim csources dist/nimble NimBinaries
           echo '${{ github.workspace }}/nim/bin' >> $GITHUB_PATH
 
       - name: Run nim-ethash tests
diff --git a/.gitignore b/.gitignore
index 5f56dbf..22fd483 100644
--- a/.gitignore
+++ b/.gitignore
@@ -5,4 +5,5 @@ nimcache/
 build/
 *.so
 *.dylib
-*.a
\ No newline at end of file
+*.a
+*.exe
diff --git a/src/private/intmath.nim b/src/private/intmath.nim
index 0299f8a..9108eb4 100644
--- a/src/private/intmath.nim
+++ b/src/private/intmath.nim
@@ -24,8 +24,8 @@ proc bit_length*[T: SomeInteger](n: T): T =
   ## Calculates how many bits are necessary to represent the number
 
   when withBuiltins and T is TbuiltinSupported:
-    result = if n == T(0): 0                    # Removing this branch would make divmod 4x faster :/
-             else: T.sizeof * 8 - builtin_clz(n)
+    result = if n == T(0): 0.T                    # Removing this branch would make divmod 4x faster :/
+             else: T(T.sizeof) * 8.T - builtin_clz(n).T
 
   else:
     var x = n
diff --git a/tests/test_internal_multiprecision_arithmetic.nim b/tests/test_internal_multiprecision_arithmetic.nim
index 5cf4aaa..2ac2386 100644
--- a/tests/test_internal_multiprecision_arithmetic.nim
+++ b/tests/test_internal_multiprecision_arithmetic.nim
@@ -11,8 +11,8 @@ suite "[Internal] Testing multi-precision arithmetic":
     randomize(42) # random seed for reproducibility
     for _ in 0 ..< 10_000_000:
       let
-        a = random(high(int)).uint64
-        b = random(high(int)).uint64
+        a = rand(high(int)).uint64
+        b = rand(high(int)).uint64
 
       check: a * b == mulCarry(a, b).unit