diff --git a/.circleci/config.yml b/.circleci/config.yml
index c0e79f4fe..2868edc64 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -17,7 +17,7 @@ jobs:
             # Set up the Debian testing repo, and then install g++ from there...
             sudo bash -c "echo \"deb http://ftp.us.debian.org/debian testing main contrib non-free\" >> /etc/apt/sources.list"
             sudo apt-get update
-            sudo apt-get install node-less cmake build-essential clang-format-6.0 flake8 uglifyjs python3-yaml chromium
+            sudo apt-get install node-less cmake build-essential clang-format-6.0 flake8 uglifyjs python3-yaml chromium ccache
             sudo apt-get install -t testing g++-8
             sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-6 60 --slave /usr/bin/g++ g++ /usr/bin/g++-6
             sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-8 80 --slave /usr/bin/g++ g++ /usr/bin/g++-8
@@ -47,18 +47,20 @@ jobs:
 
       - restore_cache:
           keys:
-          - v1-emsdk-{{ checksum "emsdk/Makefile" }}-v4
+          - v1-emsdk-{{ checksum "emsdk/Makefile" }}-v6
 
       - run:
           name: build
           no_output_timeout: 1200
           command: |
             make
+            ccache -s
 
       - save_cache:
           paths:
             - ./emsdk/emsdk
-          key: v1-emsdk-{{ checksum "emsdk/Makefile" }}-v4
+            - ~/.ccache
+          key: v1-emsdk-{{ checksum "emsdk/Makefile" }}-v6
 
       - run:
           name: test
diff --git a/.gitignore b/.gitignore
index 31de30260..92dbc2d7c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -13,6 +13,7 @@ build
 downloads
 host
 installs
+ccache
 
 /root/
 /build/
diff --git a/Makefile b/Makefile
index e79b64763..7009df95e 100644
--- a/Makefile
+++ b/Makefile
@@ -29,6 +29,7 @@ LDFLAGS=\
   -s WASM=1 \
 	-s SWAPPABLE_ASM_MODULE=1 \
 	-s USE_FREETYPE=1 \
+	-s USE_LIBPNG=1 \
 	-std=c++14 \
   -lstdc++ \
   --memory-init-file 0
@@ -126,7 +127,7 @@ clean:
 
 
 %.bc: %.c $(CPYTHONLIB)
-	$(CC) -o $@ $< $(CFLAGS)
+	$(CC) -o $@ -c $< $(CFLAGS)
 
 
 build/test.data: $(CPYTHONLIB)
@@ -161,7 +162,25 @@ root/.built: \
 	touch root/.built
 
 
-$(CPYTHONLIB): emsdk/emsdk/.complete
+ccache/emcc:
+	if hash ccache &>/dev/null; then \
+		mkdir -p $(PYODIDE_ROOT)/ccache ; \
+    ln -s `which ccache` $(PYODIDE_ROOT)/ccache/emcc ; \
+  else \
+    ln -s emsdk/emsdk/emscripten/tag-1.38.4/emcc $(PYODIDE_ROOT)/ccache/emcc; \
+  fi
+
+
+ccache/em++:
+	if hash ccache &>/dev/null; then \
+		mkdir -p $(PYODIDE_ROOT)/ccache ; \
+    ln -s `which ccache` $(PYODIDE_ROOT)/ccache/em++ ; \
+  else \
+    ln -s emsdk/emsdk/emscripten/tag-1.38.4/em++ $(PYODIDE_ROOT)/ccache/em++; \
+  fi
+
+
+$(CPYTHONLIB): emsdk/emsdk/.complete ccache/emcc ccache/em++
 	make -C $(CPYTHONROOT)
 
 
diff --git a/Makefile.envs b/Makefile.envs
index 2f1bf651e..b94e90988 100644
--- a/Makefile.envs
+++ b/Makefile.envs
@@ -1,4 +1,4 @@
-export PATH := $(PYODIDE_ROOT)/emsdk/emsdk:$(PYODIDE_ROOT)/emsdk/emsdk/clang/tag-e-1.38.4/build_tag-e1.38.4_64/bin:$(PYODIDE_ROOT)/emsdk/emsdk/node/8.9.1_64bit/bin:$(PYODIDE_ROOT)/emsdk/emsdk/emscripten/tag-1.38.4:$(PYODIDE_ROOT)/emsdk/emsdk/binaryen/tag-1.38.4_64bit_binaryen/bin:$(PATH)
+export PATH := $(PYODIDE_ROOT)/ccache:$(PYODIDE_ROOT)/emsdk/emsdk:$(PYODIDE_ROOT)/emsdk/emsdk/clang/tag-e-1.38.4/build_tag-e1.38.4_64/bin:$(PYODIDE_ROOT)/emsdk/emsdk/node/8.9.1_64bit/bin:$(PYODIDE_ROOT)/emsdk/emsdk/emscripten/tag-1.38.4:$(PYODIDE_ROOT)/emsdk/emsdk/binaryen/tag-1.38.4_64bit_binaryen/bin:$(PATH)
 
 export EMSDK = $(PYODIDE_ROOT)/emsdk/emsdk
 export EM_CONFIG = $(PYODIDE_ROOT)/emsdk/emsdk/.emscripten
diff --git a/README.md b/README.md
index f50e64b37..268685f3c 100644
--- a/README.md
+++ b/README.md
@@ -28,6 +28,8 @@ Additional build prerequisites are:
 - PyYAML
 - [lessc](https://lesscss.org/) to compile less to css.
 - [uglifyjs](https://github.com/mishoo/UglifyJS) to minify Javascript builds.
+- [ccache](https://ccache.samba.org) (optional) recommended for much faster rebuilds.
+
 
 `make`
 
diff --git a/cpython/Setup.local b/cpython/Setup.local
index 24278bb01..80517c913 100644
--- a/cpython/Setup.local
+++ b/cpython/Setup.local
@@ -24,7 +24,7 @@ _posixsubprocess _posixsubprocess.c
 
 binascii binascii.c
 
-zlib zlibmodule.c -IModules/zlib zlib/adler32.c zlib/crc32.c zlib/deflate.c zlib/infback.c zlib/inffast.c zlib/inflate.c zlib/inftrees.c zlib/trees.c zlib/zutil.c zlib/compress.c zlib/uncompr.c zlib/gzclose.c zlib/gzlib.c zlib/gzread.c zlib/gzwrite.c
+zlib zlibmodule.c -IModules/zlib
 
 pyexpat expat/xmlparse.c expat/xmlrole.c expat/xmltok.c pyexpat.c -I$(srcdir)/Modules/expat -DHAVE_EXPAT_CONFIG_H -DUSE_PYEXPAT_CAPI -DXML_POOR_ENTROPY
 
diff --git a/test/test_python.py b/test/test_python.py
index 4647cfda8..78fde14c2 100644
--- a/test/test_python.py
+++ b/test/test_python.py
@@ -1,3 +1,4 @@
+import os
 import pathlib
 import time
 
@@ -286,7 +287,7 @@ def test_run_core_python_test(python_test, selenium):
 def pytest_generate_tests(metafunc):
     if 'python_test' in metafunc.fixturenames:
         test_modules = []
-        if True:
+        if 'CIRCLECI' not in os.environ:
             with open(
                     str(pathlib.Path(__file__).parents[0] /
                         "python_tests.txt")) as fp: