diff --git a/plugins/python-build/bin/pyenv-install b/plugins/python-build/bin/pyenv-install
index cb6cf623..1c30ac8c 100755
--- a/plugins/python-build/bin/pyenv-install
+++ b/plugins/python-build/bin/pyenv-install
@@ -6,16 +6,17 @@
 #        pyenv install [-f] [-kvp] <definition-file>
 #        pyenv install -l|--list
 #
-#   -l/--list        List all available versions
-#   -f/--force       Install even if the version appears to be installed already
+#   -l/--list          List all available versions
+#   -f/--force         Install even if the version appears to be installed already
+#   -s/--skip-existing Skip if the version appears to be installed already
 #
 #   python-build options:
 #
-#   -k/--keep        Keep source tree in $PYENV_BUILD_ROOT after installation
-#                    (defaults to $PYENV_ROOT/sources)
-#   -v/--verbose     Verbose mode: print compilation status to stdout
-#   -p/--patch       Apply a patch from stdin before building
-#   -g/--debug       Build a debug version
+#   -k/--keep          Keep source tree in $PYENV_BUILD_ROOT after installation
+#                      (defaults to $PYENV_ROOT/sources)
+#   -v/--verbose       Verbose mode: print compilation status to stdout
+#   -p/--patch         Apply a patch from stdin before building
+#   -g/--debug         Build a debug version
 #
 # For detailed information on installing Python versions with
 # python-build, including a list of environment variables for adjusting
@@ -52,6 +53,7 @@ indent() {
 }
 
 unset FORCE
+unset SKIP_EXISTING
 unset KEEP
 unset VERBOSE
 unset HAS_PATCH
@@ -71,6 +73,9 @@ for option in "${OPTIONS[@]}"; do
   "f" | "force" )
     FORCE=true
     ;;
+  "s" | "skip-existing" )
+    SKIP_EXISTING=true
+    ;;
   "k" | "keep" )
     [ -n "${PYENV_BUILD_ROOT}" ] || PYENV_BUILD_ROOT="${PYENV_ROOT}/sources"
     ;;
@@ -134,14 +139,21 @@ PREFIX="${PYENV_ROOT}/versions/${VERSION_NAME}"
 
 # If the installation prefix exists, prompt for confirmation unless
 # the --force option was specified.
-if [ -z "$FORCE" ] && [ -d "${PREFIX}/bin" ]; then
-  echo "pyenv: $PREFIX already exists" >&2
-  read -p "continue with installation? (y/N) "
+if [ -d "${PREFIX}/bin" ]; then
+  if [ -z "$FORCE" ] && [ -z "$SKIP_EXISTING" ]; then
+    echo "pyenv: $PREFIX already exists" >&2
+    read -p "continue with installation? (y/N) "
 
-  case "$REPLY" in
-  y* | Y* ) ;;
-  * ) exit 1 ;;
-  esac
+    case "$REPLY" in
+    y* | Y* ) ;;
+    * ) exit 1 ;;
+    esac
+  elif [ -n "$SKIP_EXISTING" ]; then
+    # Since we know the python version is already installed, and are opting to
+    # not force installation of existing versions, we just `exit 0` here to
+    # leave things happy
+    exit 0
+  fi
 fi
 
 # If PYENV_BUILD_ROOT is set, always pass keep options to python-build.
@@ -158,7 +170,7 @@ fi
 
 # Default PYENV_VERSION to the friendly Python version. (The
 # CPython installer requires an existing Python installation to run. An
-# unsatisfied local python version can cause the installer to
+# unsatisfied local .python-version file can cause the installer to
 # fail.)
 if [[ "${VERSION_NAME}" == [23]"."* ]]; then
   for version in "${VERSION_NAME%-dev}" "${VERSION_NAME%.*}" "${VERSION_NAME%%.*}"; do
diff --git a/plugins/python-build/bin/python-build b/plugins/python-build/bin/python-build
index 638879bc..13bc3264 100755
--- a/plugins/python-build/bin/python-build
+++ b/plugins/python-build/bin/python-build
@@ -1,6 +1,6 @@
 #!/usr/bin/env bash
 
-PYTHON_BUILD_VERSION="20140225"
+PYTHON_BUILD_VERSION="20140408"
 
 set -E
 exec 3<&2 # preserve original stderr at fd 3
@@ -245,7 +245,7 @@ http_head_curl() {
 }
 
 http_get_curl() {
-  curl -C - -o "${2:--}" -qsSLf "$1"
+  curl -q -o "${2:--}" -sSLf "$1"
 }
 
 http_head_wget() {
@@ -253,7 +253,7 @@ http_head_wget() {
 }
 
 http_get_wget() {
-  wget -nv -c -O "${2:--}" "$1"
+  wget -nv -O "${2:--}" "$1"
 }
 
 fetch_tarball() {
@@ -283,7 +283,7 @@ fetch_tarball() {
     tar_args="${tar_args/z/j}"
   fi
 
-  if ! symlink_tarball_from_cache "$package_filename" "$checksum"; then
+  if ! reuse_existing_tarball "$package_filename" "$checksum"; then
     echo "Downloading ${package_filename}..." >&2
     http head "$mirror_url" &&
     download_tarball "$mirror_url" "$package_filename" "$checksum" ||
@@ -300,13 +300,19 @@ fetch_tarball() {
   } >&4 2>&1
 }
 
-symlink_tarball_from_cache() {
-  [ -n "$PYTHON_BUILD_CACHE_PATH" ] || return 1
-
+reuse_existing_tarball() {
   local package_filename="$1"
-  local cached_package_filename="${PYTHON_BUILD_CACHE_PATH}/$package_filename"
   local checksum="$2"
 
+  # Reuse existing file in build location
+  if [ -e "$package_filename" ] && verify_checksum "$package_filename" "$checksum"; then
+    return 0
+  fi
+
+  # Reuse previously downloaded file in cache location
+  [ -n "$PYTHON_BUILD_CACHE_PATH" ] || return 1
+  local cached_package_filename="${PYTHON_BUILD_CACHE_PATH}/$package_filename"
+
   [ -e "$cached_package_filename" ] || return 1
   verify_checksum "$cached_package_filename" "$checksum" >&4 2>&1 || return 1
   ln -s "$cached_package_filename" "$package_filename" >&4 2>&1 || return 1
@@ -429,7 +435,7 @@ fetch_jar() {
 
   local package_filename="${package_name}.jar"
 
-  if ! symlink_tarball_from_cache "$package_filename" "$checksum"; then
+  if ! reuse_existing_tarball "$package_filename" "$checksum"; then
     echo "Downloading ${package_filename}..." >&2
     http head "$mirror_url" &&
     download_tarball "$mirror_url" "$package_filename" "$checksum" ||
@@ -463,7 +469,7 @@ fetch_zip() {
 
   local package_filename="${package_name}.zip"
 
-  if ! symlink_tarball_from_cache "$package_filename" "$checksum"; then
+  if ! reuse_existing_tarball "$package_filename" "$checksum"; then
     echo "Downloading ${package_filename}..." >&2
     http head "$mirror_url" &&
     download_tarball "$mirror_url" "$package_filename" "$checksum" ||
@@ -497,7 +503,7 @@ fetch_script() {
 
   local package_filename="${package_name}.sh" # TODO: extract suffix from ${package_url}
 
-  if ! symlink_tarball_from_cache "$package_filename" "$checksum"; then
+  if ! reuse_existing_tarball "$package_filename" "$checksum"; then
     echo "Downloading ${package_filename}..." >&2
     http head "$mirror_url" &&
     download_tarball "$mirror_url" "$package_filename" "$checksum" ||
@@ -860,7 +866,9 @@ fix_rbx_gem_binstubs() {
     for file in "$gemdir"/*; do
       binstub="${bindir}/${file##*/}"
       rm -f "$binstub"
-      sed -E "s:^#\!.+:#\!${bindir}/ruby:" < "$file" > "$binstub"
+      { echo "#!${bindir}/ruby"
+        cat "$file"
+      } > "$binstub"
       chmod +x "$binstub"
     done
     rm -rf "$gemdir"
diff --git a/plugins/python-build/test/build.bats b/plugins/python-build/test/build.bats
index e5c15d2e..23ed87a2 100644
--- a/plugins/python-build/test/build.bats
+++ b/plugins/python-build/test/build.bats
@@ -56,7 +56,7 @@ assert_build_log() {
 }
 
 @test "yaml is installed for python" {
-  cached_tarball "yaml-0.1.5"
+  cached_tarball "yaml-0.1.6"
   cached_tarball "Python-3.2.1"
 
   stub brew false
@@ -69,7 +69,7 @@ assert_build_log() {
   unstub make
 
   assert_build_log <<OUT
-yaml-0.1.5: --prefix=$INSTALL_ROOT --libdir=$INSTALL_ROOT/lib
+yaml-0.1.6: --prefix=$INSTALL_ROOT --libdir=$INSTALL_ROOT/lib
 make -j 2
 make install
 Python-3.2.1: --prefix=$INSTALL_ROOT --libdir=$INSTALL_ROOT/lib
@@ -79,7 +79,7 @@ OUT
 }
 
 @test "apply python patch before building" {
-  cached_tarball "yaml-0.1.5"
+  cached_tarball "yaml-0.1.6"
   cached_tarball "Python-3.2.1"
 
   stub brew false
@@ -94,7 +94,7 @@ OUT
   unstub patch
 
   assert_build_log <<OUT
-yaml-0.1.5: --prefix=$INSTALL_ROOT --libdir=$INSTALL_ROOT/lib
+yaml-0.1.6: --prefix=$INSTALL_ROOT --libdir=$INSTALL_ROOT/lib
 make -j 2
 make install
 patch -p0 -i -
@@ -153,6 +153,7 @@ OUT
 @test "readline is not linked from Homebrew when explicitly defined" {
   cached_tarball "Python-3.2.1"
 
+  # python-build
   readline_libdir="$TMP/custom"
   mkdir -p "$readline_libdir/include/readline"
   touch "$readline_libdir/include/readline/rlconf.h"
diff --git a/plugins/python-build/test/cache.bats b/plugins/python-build/test/cache.bats
index a5ff8338..e5bacb53 100644
--- a/plugins/python-build/test/cache.bats
+++ b/plugins/python-build/test/cache.bats
@@ -11,7 +11,7 @@ setup() {
 
 @test "packages are saved to download cache" {
   stub md5 true
-  stub curl "-C - -o * -*S* http://example.com/* : cp $FIXTURE_ROOT/\${6##*/} \$4"
+  stub curl "-q -o * -*S* http://example.com/* : cp $FIXTURE_ROOT/\${5##*/} \$3"
 
   install_fixture definitions/without-checksum
   [ "$status" -eq 0 ]
@@ -59,7 +59,7 @@ setup() {
 
   stub md5 true "echo invalid" "echo $checksum"
   stub curl "-*I* : true" \
-    "-C - -o * -*S* http://?*/$checksum : cp $FIXTURE_ROOT/package-1.0.0.tar.gz \$4"
+    "-q -o * -*S* http://?*/$checksum : cp $FIXTURE_ROOT/package-1.0.0.tar.gz \$3"
 
   touch "${PYTHON_BUILD_CACHE_PATH}/package-1.0.0.tar.gz"
 
@@ -76,7 +76,7 @@ setup() {
 
 @test "nonexistent cache directory is ignored" {
   stub md5 true
-  stub curl "-C - -o * -*S* http://example.com/* : cp $FIXTURE_ROOT/\${6##*/} \$4"
+  stub curl "-q -o * -*S* http://example.com/* : cp $FIXTURE_ROOT/\${5##*/} \$3"
 
   export PYTHON_BUILD_CACHE_PATH="${TMP}/nonexistent"
 
diff --git a/plugins/python-build/test/checksum.bats b/plugins/python-build/test/checksum.bats
index 8b16c01a..33261fd1 100644
--- a/plugins/python-build/test/checksum.bats
+++ b/plugins/python-build/test/checksum.bats
@@ -7,7 +7,7 @@ export PYTHON_BUILD_CACHE_PATH=
 
 @test "package URL without checksum" {
   stub md5 true
-  stub curl "-C - -o * -*S* http://example.com/* : cp $FIXTURE_ROOT/\${6##*/} \$4"
+  stub curl "-q -o * -*S* http://example.com/* : cp $FIXTURE_ROOT/\${5##*/} \$3"
 
   install_fixture definitions/without-checksum
   [ "$status" -eq 0 ]
@@ -20,7 +20,7 @@ export PYTHON_BUILD_CACHE_PATH=
 
 @test "package URL with valid checksum" {
   stub md5 true "echo 83e6d7725e20166024a1eb74cde80677"
-  stub curl "-C - -o * -*S* http://example.com/* : cp $FIXTURE_ROOT/\${6##*/} \$4"
+  stub curl "-q -o * -*S* http://example.com/* : cp $FIXTURE_ROOT/\${5##*/} \$3"
 
   install_fixture definitions/with-checksum
   [ "$status" -eq 0 ]
@@ -33,7 +33,7 @@ export PYTHON_BUILD_CACHE_PATH=
 
 @test "package URL with invalid checksum" {
   stub md5 true "echo 83e6d7725e20166024a1eb74cde80677"
-  stub curl "-C - -o * -*S* http://example.com/* : cp $FIXTURE_ROOT/\${6##*/} \$4"
+  stub curl "-q -o * -*S* http://example.com/* : cp $FIXTURE_ROOT/\${5##*/} \$3"
 
   install_fixture definitions/with-invalid-checksum
   [ "$status" -eq 1 ]
@@ -46,7 +46,7 @@ export PYTHON_BUILD_CACHE_PATH=
 
 @test "package URL with checksum but no MD5 support" {
   stub md5 false
-  stub curl "-C - -o * -*S* http://example.com/* : cp $FIXTURE_ROOT/\${6##*/} \$4"
+  stub curl "-q -o * -*S* http://example.com/* : cp $FIXTURE_ROOT/\${5##*/} \$3"
 
   install_fixture definitions/with-checksum
   [ "$status" -eq 0 ]
@@ -59,7 +59,7 @@ export PYTHON_BUILD_CACHE_PATH=
 
 @test "package with invalid checksum" {
   stub md5 true "echo invalid"
-  stub curl "-C - -o * -*S* http://example.com/* : cp $FIXTURE_ROOT/\${6##*/} \$4"
+  stub curl "-q -o * -*S* http://example.com/* : cp $FIXTURE_ROOT/\${5##*/} \$3"
 
   install_fixture definitions/with-checksum
   [ "$status" -eq 1 ]
@@ -68,3 +68,46 @@ export PYTHON_BUILD_CACHE_PATH=
   unstub curl
   unstub md5
 }
+
+@test "existing tarball in build location is reused" {
+  stub md5 true "echo 83e6d7725e20166024a1eb74cde80677"
+  stub curl false
+  stub wget false
+
+  export -n PYTHON_BUILD_CACHE_PATH
+  export PYTHON_BUILD_BUILD_PATH="${TMP}/build"
+
+  mkdir -p "$PYTHON_BUILD_BUILD_PATH"
+  ln -s "${FIXTURE_ROOT}/package-1.0.0.tar.gz" "$PYTHON_BUILD_BUILD_PATH"
+
+  run_inline_definition <<DEF
+install_package "package-1.0.0" "http://example.com/packages/package-1.0.0.tar.gz#83e6d7725e20166024a1eb74cde80677" copy
+DEF
+
+  assert_success
+  [ -x "${INSTALL_ROOT}/bin/package" ]
+
+  unstub md5
+}
+
+@test "existing tarball in build location is discarded if not matching checksum" {
+  stub md5 true \
+    "echo invalid" \
+    "echo 83e6d7725e20166024a1eb74cde80677"
+  stub curl "-q -o * -*S* http://example.com/* : cp $FIXTURE_ROOT/\${5##*/} \$3"
+
+  export -n PYTHON_BUILD_CACHE_PATH
+  export PYTHON_BUILD_BUILD_PATH="${TMP}/build"
+
+  mkdir -p "$PYTHON_BUILD_BUILD_PATH"
+  touch "${PYTHON_BUILD_BUILD_PATH}/package-1.0.0.tar.gz"
+
+  run_inline_definition <<DEF
+install_package "package-1.0.0" "http://example.com/packages/package-1.0.0.tar.gz#83e6d7725e20166024a1eb74cde80677" copy
+DEF
+
+  assert_success
+  [ -x "${INSTALL_ROOT}/bin/package" ]
+
+  unstub md5
+}
diff --git a/plugins/python-build/test/fixtures/definitions/needs-yaml b/plugins/python-build/test/fixtures/definitions/needs-yaml
index deae9631..76c57957 100644
--- a/plugins/python-build/test/fixtures/definitions/needs-yaml
+++ b/plugins/python-build/test/fixtures/definitions/needs-yaml
@@ -1,2 +1,2 @@
-install_package "yaml-0.1.5" "http://pyyaml.org/download/libyaml/yaml-0.1.5.tar.gz" --if needs_yaml
+install_package "yaml-0.1.6" "http://pyyaml.org/download/libyaml/yaml-0.1.6.tar.gz" --if needs_yaml
 install_package "Python-3.2.1" "http://python.org/ftp/python/3.2.1/Python-3.2.1.tar.gz"
diff --git a/plugins/python-build/test/mirror.bats b/plugins/python-build/test/mirror.bats
index fbd9ab87..a7621088 100644
--- a/plugins/python-build/test/mirror.bats
+++ b/plugins/python-build/test/mirror.bats
@@ -8,7 +8,7 @@ export PYTHON_BUILD_MIRROR_URL=http://mirror.example.com
 
 @test "package URL without checksum bypasses mirror" {
   stub md5 true
-  stub curl "-C - -o * -*S* http://example.com/* : cp $FIXTURE_ROOT/\${6##*/} \$4"
+  stub curl "-q -o * -*S* http://example.com/* : cp $FIXTURE_ROOT/\${5##*/} \$3"
 
   install_fixture definitions/without-checksum
   echo "$output" >&2
@@ -22,7 +22,7 @@ export PYTHON_BUILD_MIRROR_URL=http://mirror.example.com
 
 @test "package URL with checksum but no MD5 support bypasses mirror" {
   stub md5 false
-  stub curl "-C - -o * -*S* http://example.com/* : cp $FIXTURE_ROOT/\${6##*/} \$4"
+  stub curl "-q -o * -*S* http://example.com/* : cp $FIXTURE_ROOT/\${5##*/} \$3"
 
   install_fixture definitions/with-checksum
   [ "$status" -eq 0 ]
@@ -39,7 +39,7 @@ export PYTHON_BUILD_MIRROR_URL=http://mirror.example.com
 
   stub md5 true "echo $checksum"
   stub curl "-*I* $mirror_url : true" \
-    "-C - -o * -*S* $mirror_url : cp $FIXTURE_ROOT/package-1.0.0.tar.gz \$4"
+    "-q -o * -*S* $mirror_url : cp $FIXTURE_ROOT/package-1.0.0.tar.gz \$3"
 
   install_fixture definitions/with-checksum
   [ "$status" -eq 0 ]
@@ -56,7 +56,7 @@ export PYTHON_BUILD_MIRROR_URL=http://mirror.example.com
 
   stub md5 true "echo $checksum"
   stub curl "-*I* $mirror_url : false" \
-    "-C - -o * -*S* http://example.com/* : cp $FIXTURE_ROOT/\${6##*/} \$4"
+    "-q -o * -*S* http://example.com/* : cp $FIXTURE_ROOT/\${5##*/} \$3"
 
   install_fixture definitions/with-checksum
   [ "$status" -eq 0 ]
@@ -73,8 +73,8 @@ export PYTHON_BUILD_MIRROR_URL=http://mirror.example.com
 
   stub md5 true "echo invalid" "echo $checksum"
   stub curl "-*I* $mirror_url : true" \
-    "-C - -o * -*S* $mirror_url : cp $FIXTURE_ROOT/package-1.0.0.tar.gz \$4" \
-    "-C - -o * -*S* http://example.com/* : cp $FIXTURE_ROOT/\${6##*/} \$4"
+    "-q -o * -*S* $mirror_url : cp $FIXTURE_ROOT/package-1.0.0.tar.gz \$3" \
+    "-q -o * -*S* http://example.com/* : cp $FIXTURE_ROOT/\${5##*/} \$3"
 
   install_fixture definitions/with-checksum
   echo "$output" >&2
@@ -92,7 +92,7 @@ export PYTHON_BUILD_MIRROR_URL=http://mirror.example.com
 
   stub md5 true "echo $checksum"
   stub curl "-*I* : true" \
-    "-C - -o * -*S* http://?*/$checksum : cp $FIXTURE_ROOT/package-1.0.0.tar.gz \$4" \
+    "-q -o * -*S* http://?*/$checksum : cp $FIXTURE_ROOT/package-1.0.0.tar.gz \$3" \
 
   install_fixture definitions/with-checksum
   [ "$status" -eq 0 ]