diff --git a/.github/workflows/arm.yml b/.github/workflows/arm.yml
index d7f8964e..2375f43c 100644
--- a/.github/workflows/arm.yml
+++ b/.github/workflows/arm.yml
@@ -13,7 +13,7 @@ jobs:
         env:
           - { TARGET_HOST: "arm-linux-gnueabihf" }
     env: ${{ matrix.env }}
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     steps:
     - uses: actions/checkout@v2
 
diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 516dca1a..adfc5ca1 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -15,7 +15,7 @@ jobs:
           - { CC: "clang", CXX: "clang++" }
           - { CMAKE: "cmake" }
     env: ${{ matrix.env }}
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     steps:
     - uses: actions/checkout@v2
 
diff --git a/.github/workflows/coverity.yml b/.github/workflows/coverity.yml
index 38ec1288..b442a542 100644
--- a/.github/workflows/coverity.yml
+++ b/.github/workflows/coverity.yml
@@ -6,7 +6,7 @@ on:
 
 jobs:
   scan:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     env:
       TOKEN: ${{ secrets.COVERITY_SCAN_TOKEN }}
     steps:
diff --git a/.github/workflows/decode.yml b/.github/workflows/decode.yml
index 34f279bb..7114c8dc 100644
--- a/.github/workflows/decode.yml
+++ b/.github/workflows/decode.yml
@@ -27,7 +27,7 @@ jobs:
           - { DECODESTREAMS: "libde265-teststreams-wpp-nolf" }
           - { DECODESTREAMS: "libde265-teststreams-wpp-nolf", THREADING: "--single-threaded" }
     env: ${{ matrix.env }}
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     continue-on-error: true
     steps:
     - uses: actions/checkout@v2
diff --git a/appveyor.yml b/appveyor.yml
index b584c707..8903ecca 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -25,13 +25,13 @@ install:
 
 build_script:
   - ps: if($env:PLATFORM -eq "x64") { $env:CMAKE_GEN_SUFFIX=" Win64" }
-  - cmake "-G%GENERATOR%%CMAKE_GEN_SUFFIX%" -H. -Bbuild
+  - cmake "-G%GENERATOR%%CMAKE_GEN_SUFFIX%" -H. -Bbuild -DENABLE_ENCODER=ON
   - cmake --build build --config %CONFIGURATION%
 
 before_test:
   - copy /y build\dec265\%CONFIGURATION%\dec265.exe build
   - copy /y build\enc265\%CONFIGURATION%\enc265.exe build
-  - copy /y build\libde265\%CONFIGURATION%\libde265.dll build
+  - copy /y build\libde265\%CONFIGURATION%\de265.dll build
 
 test_script:
   - build\dec265.exe -q -c -f 100 libde265-data\IDR-only\paris-352x288-intra.bin
diff --git a/libde265/decctx.cc b/libde265/decctx.cc
index 6e96c402..b46d97a5 100644
--- a/libde265/decctx.cc
+++ b/libde265/decctx.cc
@@ -265,6 +265,7 @@ decoder_context::decoder_context()
   prevPicOrderCntLsb = 0;
   prevPicOrderCntMsb = 0;
   img = NULL;
+  previous_slice_header = nullptr;
 
   /*
   int PocLsbLt[MAX_NUM_REF_PICS];
diff --git a/libde265/decctx.h b/libde265/decctx.h
index c249c01e..0022cdf0 100644
--- a/libde265/decctx.h
+++ b/libde265/decctx.h
@@ -450,7 +450,7 @@ class decoder_context : public base_context {
   de265_image* img;
 
  public:
-  const slice_segment_header* previous_slice_header = nullptr; /* Remember the last slice for a successive
+  const slice_segment_header* previous_slice_header; /* Remember the last slice for a successive
 								  dependent slice. */
 
 
diff --git a/libde265/motion.cc b/libde265/motion.cc
index 45d547b0..c3c7f7b6 100644
--- a/libde265/motion.cc
+++ b/libde265/motion.cc
@@ -1642,8 +1642,8 @@ void derive_spatial_luma_vector_prediction(base_context* ctx,
 
     out_availableFlagLXN[0] = false;
     out_availableFlagLXN[1] = false;
-    out_mvLXN[0] = MotionVector{};
-    out_mvLXN[1] = MotionVector{};
+    out_mvLXN[0] = MotionVector();
+    out_mvLXN[1] = MotionVector();
     return;
   }
 
diff --git a/scripts/ci-before-install-linux.sh b/scripts/ci-before-install-linux.sh
index cf781c09..5a6b5923 100755
--- a/scripts/ci-before-install-linux.sh
+++ b/scripts/ci-before-install-linux.sh
@@ -85,6 +85,11 @@ if [ ! -z "$CMAKE" ]; then
         "
 fi
 
+# Workaround issues where the "azure.archive.ubuntu.com" mirror is not available
+# See https://github.com/actions/runner-images/issues/675
+sudo sed -i 's/azure\.//' /etc/apt/sources.list
+UPDATE_APT=1
+
 if [ ! -z "$UPDATE_APT" ]; then
     echo "Updating package lists ..."
     sudo apt-get update -qq