diff --git a/src/ci/docker/host-x86_64/dist-x86_64-freebsd/Dockerfile b/src/ci/docker/host-x86_64/dist-x86_64-freebsd/Dockerfile
index f42e6f770ebe8..e62aa74662bed 100644
--- a/src/ci/docker/host-x86_64/dist-x86_64-freebsd/Dockerfile
+++ b/src/ci/docker/host-x86_64/dist-x86_64-freebsd/Dockerfile
@@ -35,10 +35,9 @@ ENV \
 
 ENV HOSTS=x86_64-unknown-freebsd
 
-ENV RUST_CONFIGURE_ARGS \
-    --enable-full-tools \
+ENV RUST_CONFIGURE_ARGS="--enable-full-tools \
     --enable-extended \
     --enable-profiler \
     --enable-sanitizers \
-    --disable-docs
-ENV SCRIPT python3 ../x.py dist --host $HOSTS --target $HOSTS
+    --disable-docs"
+ENV SCRIPT="python3 ../x.py dist --host $HOSTS --target $HOSTS"
diff --git a/src/ci/docker/host-x86_64/dist-x86_64-illumos/Dockerfile b/src/ci/docker/host-x86_64/dist-x86_64-illumos/Dockerfile
index 37a8dc56a5fa6..0675c3cafd9e7 100644
--- a/src/ci/docker/host-x86_64/dist-x86_64-illumos/Dockerfile
+++ b/src/ci/docker/host-x86_64/dist-x86_64-illumos/Dockerfile
@@ -36,5 +36,5 @@ ENV \
 
 ENV HOSTS=x86_64-unknown-illumos
 
-ENV RUST_CONFIGURE_ARGS --enable-extended --disable-docs
-ENV SCRIPT python2.7 ../x.py dist --host $HOSTS --target $HOSTS
+ENV RUST_CONFIGURE_ARGS="--enable-extended --disable-docs"
+ENV SCRIPT="python2.7 ../x.py dist --host $HOSTS --target $HOSTS"
diff --git a/src/ci/docker/host-x86_64/dist-x86_64-linux/Dockerfile b/src/ci/docker/host-x86_64/dist-x86_64-linux/Dockerfile
index cb57478761994..b168c739c9793 100644
--- a/src/ci/docker/host-x86_64/dist-x86_64-linux/Dockerfile
+++ b/src/ci/docker/host-x86_64/dist-x86_64-linux/Dockerfile
@@ -80,8 +80,7 @@ ENV PGO_HOST=x86_64-unknown-linux-gnu
 
 ENV HOSTS=x86_64-unknown-linux-gnu
 
-ENV RUST_CONFIGURE_ARGS \
-      --enable-full-tools \
+ENV RUST_CONFIGURE_ARGS="--enable-full-tools \
       --enable-sanitizers \
       --enable-profiler \
       --enable-compiler-docs \
@@ -94,23 +93,23 @@ ENV RUST_CONFIGURE_ARGS \
       --set rust.jemalloc \
       --set rust.bootstrap-override-lld=true \
       --set rust.lto=thin \
-      --set rust.codegen-units=1
+      --set rust.codegen-units=1"
 
 COPY host-x86_64/dist-x86_64-linux/dist.sh /scripts/
 COPY host-x86_64/dist-x86_64-linux/dist-alt.sh /scripts/
 
-ENV SCRIPT "Must specify DOCKER_SCRIPT for this image"
+ENV SCRIPT="Must specify DOCKER_SCRIPT for this image"
 
 ENV CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_LINKER=clang
 
 # This is the only builder which will create source tarballs
-ENV DIST_SRC 1
+ENV DIST_SRC="1"
 
 # When we build cargo in this container, we don't want it to use the system
 # libcurl, instead it should compile its own.
-ENV LIBCURL_NO_PKG_CONFIG 1
+ENV LIBCURL_NO_PKG_CONFIG="1"
 
-ENV DIST_REQUIRE_ALL_TOOLS 1
+ENV DIST_REQUIRE_ALL_TOOLS="1"
 
 # FIXME: Without this, LLVMgold.so incorrectly resolves to the system
 # libstdc++, instead of the one we build.
diff --git a/src/ci/docker/host-x86_64/dist-x86_64-musl/Dockerfile b/src/ci/docker/host-x86_64/dist-x86_64-musl/Dockerfile
index 32b5058bce703..68f914a81552d 100644
--- a/src/ci/docker/host-x86_64/dist-x86_64-musl/Dockerfile
+++ b/src/ci/docker/host-x86_64/dist-x86_64-musl/Dockerfile
@@ -35,14 +35,13 @@ RUN sh /scripts/sccache.sh
 
 ENV HOSTS=x86_64-unknown-linux-musl
 
-ENV RUST_CONFIGURE_ARGS \
-      --musl-root-x86_64=/usr/local/x86_64-linux-musl \
+ENV RUST_CONFIGURE_ARGS="--musl-root-x86_64=/usr/local/x86_64-linux-musl \
       --enable-extended \
       --enable-sanitizers \
       --enable-profiler \
       --enable-lld \
       --set target.x86_64-unknown-linux-musl.crt-static=false \
-      --build $HOSTS
+      --build $HOSTS"
 
 # Newer binutils broke things on some vms/distros (i.e., linking against
 # unknown relocs disabled by the following flag), so we need to go out of our
@@ -54,4 +53,4 @@ ENV CFLAGS_x86_64_unknown_linux_musl="-Wa,-mrelax-relocations=no -Wa,--compress-
     -Wl,--compress-debug-sections=none"
 
 # To run native tests replace `dist` below with `test`
-ENV SCRIPT python3 ../x.py dist --build $HOSTS
+ENV SCRIPT="python3 ../x.py dist --build $HOSTS"
diff --git a/src/ci/docker/host-x86_64/dist-x86_64-netbsd/Dockerfile b/src/ci/docker/host-x86_64/dist-x86_64-netbsd/Dockerfile
index effdc99d9a650..3bb2c7433e03c 100644
--- a/src/ci/docker/host-x86_64/dist-x86_64-netbsd/Dockerfile
+++ b/src/ci/docker/host-x86_64/dist-x86_64-netbsd/Dockerfile
@@ -22,5 +22,5 @@ ENV \
 
 ENV HOSTS=x86_64-unknown-netbsd
 
-ENV RUST_CONFIGURE_ARGS --enable-extended --disable-docs
-ENV SCRIPT python3 ../x.py dist --host $HOSTS --target $HOSTS
+ENV RUST_CONFIGURE_ARGS="--enable-extended --disable-docs"
+ENV SCRIPT="python3 ../x.py dist --host $HOSTS --target $HOSTS"
diff --git a/src/ci/docker/host-x86_64/dist-x86_64-solaris/Dockerfile b/src/ci/docker/host-x86_64/dist-x86_64-solaris/Dockerfile
index 4d77f0aad26be..b11e8cdeaa732 100644
--- a/src/ci/docker/host-x86_64/dist-x86_64-solaris/Dockerfile
+++ b/src/ci/docker/host-x86_64/dist-x86_64-solaris/Dockerfile
@@ -32,5 +32,5 @@ ENV \
 
 ENV HOSTS=x86_64-pc-solaris
 
-ENV RUST_CONFIGURE_ARGS --enable-extended --disable-docs
-ENV SCRIPT python3 ../x.py dist --host $HOSTS --target $HOSTS
+ENV RUST_CONFIGURE_ARGS="--enable-extended --disable-docs"
+ENV SCRIPT="python3 ../x.py dist --host $HOSTS --target $HOSTS"