diff --git a/.appveyor.yml b/.appveyor.yml
index 58e8dfe2b..3e05fd5c4 100644
--- a/.appveyor.yml
+++ b/.appveyor.yml
@@ -3,6 +3,9 @@ version: '{build}'
 # use an image with recent Mingw-w64 versions available on both architectures: https://www.appveyor.com/docs/windows-images-software/#mingw-msys-cygwin
 image: Visual Studio 2015
 
+cache:
+  - NimBinaries
+
 matrix:
   # We always want 32-bit and 64-bit compilation
   fast_finish: false
@@ -22,6 +25,7 @@ install:
 build_script:
   - 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
   - dir C:\mingw-w64
 
diff --git a/.travis.yml b/.travis.yml
index bb506864a..9828e5489 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,9 +1,10 @@
-language: c # or other C/C++ variants
+language: c
 
 # https://docs.travis-ci.com/user/caching/
 cache:
   directories:
     - rocksdb
+    - vendor/Nim/bin
 
 git:
   # when multiple CI builds are queued, the tested commit needs to be in the last X commits cloned with "--depth X"
@@ -23,7 +24,7 @@ matrix:
 
 install:
   # build our own rocksdb to test with a fixed version that we think works
-  - "export ROCKSDBVER=5.14.2"
+  - export ROCKSDBVER=5.14.2
   - "[ -f rocksdb/rocksdb-$ROCKSDBVER/Makefile ] || { rm -rf rocksdb ; mkdir -p rocksdb; cd rocksdb; wget https://github.com/facebook/rocksdb/archive/v$ROCKSDBVER.tar.gz && tar xvf v$ROCKSDBVER.tar.gz; cd ..; }"
   - cd rocksdb/rocksdb-$ROCKSDBVER
   - "[ -f util/build_version.cc ] || { make util/build_version.cc ; }" # use cached version if possible
diff --git a/Makefile b/Makefile
index 15396ff66..ac77b8c79 100644
--- a/Makefile
+++ b/Makefile
@@ -71,7 +71,7 @@ BUILD_NIM := echo -e $(BUILD_MSG) "Nim compiler" && \
 		sed 's/koch tools/koch --stable tools/' build_all.sh > build_all_custom.sh; \
 		sh build_all_custom.sh $(HANDLE_OUTPUT); \
 		rm build_all_custom.sh; \
-	}
+	} && cd ../..
 NIM_BINARY := $(NIM_DIR)/bin/nim$(EXE_SUFFIX)
 # md5sum - macOS is a special case
 ifeq ($(shell uname), Darwin)
@@ -79,6 +79,8 @@ ifeq ($(shell uname), Darwin)
 else
   MD5SUM := md5sum
 endif
+# AppVeyor cache of $(NIM_DIR)/bin that doesn't get unpacked after all submodules have been checked out, like on Travis
+CI_CACHE :=
 
 # debugging tools + testing tools
 TOOLS := premix persist debug dumper hunter regress tracerTestGen persistBlockTestGen
@@ -188,14 +190,17 @@ build-nim: | deps
 	+ $(BUILD_NIM)
 
 #- initialises and updates the Git submodules
+#- 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
 #- allows parallel building with the '+' prefix
-#- rebuilds the Nim compiler after the corresponding submodule is updated
+#- rebuilds the Nim compiler after the corresponding submodule is updated (keep in mind that Git doesn't preserve file timestamps)
 $(NIM_BINARY) update: | sanity-checks
 	git submodule update --init --recursive
+	[[ -n "$(CI_CACHE)" && -d "$(CI_CACHE)" ]] && cp -a "$(CI_CACHE)"/* $(NIM_DIR)/bin/ || true
 	rm -rf $(NIMBLE_DIR) nimbus.nims && $(MAKE) nimbus.nims
-	+ [[ -e $(NIM_BINARY) && $(NIM_BINARY) -nt $(NIM_DIR)/lib/system.nim ]] || { $(BUILD_NIM); }
+	+ [[ -e $(NIM_BINARY) &&  $$(stat -c%Z $(NIM_BINARY)) -gt $$(git log --pretty=format:%cd -n 1 --date=unix --  vendor/Nim) ]] || \
+		{ $(BUILD_NIM); [[ -n "$(CI_CACHE)" ]] && rm -rf "$(CI_CACHE)" && mkdir $(CI_CACHE) && cp -a $(NIM_DIR)/bin/* "$(CI_CACHE)"/ || true; }
 
 # don't use this target, or you risk updating dependency repos that are not ready to be used in Nimbus
 update-remote: