diff --git a/.appveyor.yml b/.appveyor.yml
index f0bb5815b..c92171dd3 100644
--- a/.appveyor.yml
+++ b/.appveyor.yml
@@ -9,6 +9,7 @@ environment:
 
 cache:
   - NimBinaries
+  - jsonTestsCache
 
 matrix:
   # We always want 32-bit and 64-bit compilation
@@ -27,7 +28,7 @@ install:
   - IF "%PLATFORM%" == "x64" SET PATH=C:\mingw-w64\x86_64-8.1.0-posix-seh-rt_v6-rev0\mingw64\bin;%PATH%
 
 build_script:
-  - cd C:\projects\%APPVEYOR_PROJECT_SLUG%
+  #- cd C:\projects\%APPVEYOR_PROJECT_SLUG%
   # the 32-bit build is done on a 64-bit image, so we need to override the architecture
   - mingw32-make -j2 ARCH_OVERRIDE=%PLATFORM% CI_CACHE=NimBinaries update
   - mingw32-make -j2 ARCH_OVERRIDE=%PLATFORM% fetch-dlls
@@ -38,8 +39,10 @@ test_script:
   - build\nimbus.exe --help
   - mingw32-make -j2 ARCH_OVERRIDE=%PLATFORM% test
   - IF "%PLATFORM%" == "x64" mingw32-make -j2 test-reproducibility
-  - mingw32-make -C vendor/nim-beacon-chain -j2 test
-  - mingw32-make go-checks
+  # LFS test fixtures
+  - cd vendor\nim-beacon-chain & bash scripts\process_lfs.sh ..\..\jsonTestsCache & cd ..\..
+  - mingw32-make -C vendor/nim-beacon-chain DISABLE_LFS_SCRIPT=1 -j2 test
+  #- mingw32-make go-checks
 
 deploy: off
 
diff --git a/.travis.yml b/.travis.yml
index 87005e255..35da68839 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,10 +1,11 @@
-language: c
+language: go
 
 # https://docs.travis-ci.com/user/caching/
 cache:
   directories:
     - rocksdbCache
     - vendor/Nim/bin
+    - jsonTestsCache
 
 git:
   # when multiple CI builds are queued, the tested commit needs to be in the last X commits cloned with "--depth X"
@@ -12,6 +13,9 @@ git:
   # disable LFS file downloading during regular cloning
   lfs_skip_smudge: true
 
+go:
+  - "1.12.x"
+
 matrix:
   include:
     - os: linux
@@ -26,11 +30,14 @@ install:
   # build our own rocksdb to test with a fixed version that we think works
   - ./build_rocksdb.sh rocksdbCache
 
+  # LFS test fixtures
+  - cd vendor/nim-beacon-chain; scripts/process_lfs.sh ../../jsonTestsCache; cd ../..
+
 script:
   - set -e # fail fast
   - make -j2
   - ./build/nimbus --help
   - make -j2 test test-reproducibility
-  - make -C vendor/nim-beacon-chain -j2 test
+  - make -C vendor/nim-beacon-chain DISABLE_LFS_SCRIPT=1 -j2 test
   - make go-checks
 
diff --git a/Makefile b/Makefile
index c09ddd6d7..63fc049fb 100644
--- a/Makefile
+++ b/Makefile
@@ -160,7 +160,7 @@ build-nim: | sanity-checks
 		"$(CURDIR)/build_nim.sh" "$(NIM_DIR)" ../Nim-csources ../nimble "$(CI_CACHE)"
 
 #- in case of submodule URL changes, it propagates that change in the parent repo's .git directory
-#- initialises and updates the Git submodules
+#- initialises and updates the Git submodules, avoiding automated LFS downloads
 #- manages the AppVeyor cache of Nim compiler binaries
 #- deletes the ".nimble" dir to force the execution of the "deps" target
 #- deletes and recreates "nimbus.nims" which on Windows is a copy instead of a proper symlink
@@ -168,7 +168,7 @@ build-nim: | sanity-checks
 #- rebuilds the Nim compiler if the corresponding submodule is updated
 $(NIM_BINARY) update: | sanity-checks
 	git submodule sync --quiet --recursive
-	git submodule update --init --recursive
+	export GIT_LFS_SKIP_SMUDGE=1; git submodule update --init --recursive
 	rm -rf $(NIMBLE_DIR) nimbus.nims && \
 		$(MAKE) nimbus.nims
 	+ $(MAKE) build-nim
diff --git a/vendor/nim-beacon-chain b/vendor/nim-beacon-chain
index 4daeebbf7..6a4d27f4a 160000
--- a/vendor/nim-beacon-chain
+++ b/vendor/nim-beacon-chain
@@ -1 +1 @@
-Subproject commit 4daeebbf7e1ce1e86a1acad73714ab24a2747223
+Subproject commit 6a4d27f4ac46b2b3f86b82f2bf56f97da6290007