diff --git a/azure-pipelines.yml b/azure-pipelines.yml
index ba265ee1..e13253b5 100644
--- a/azure-pipelines.yml
+++ b/azure-pipelines.yml
@@ -7,19 +7,19 @@ pr: none
 jobs:
   - job: "wasi"
     pool:
-      vmImage: "ubuntu-18.04"
+      vmImage: "ubuntu-20.04"
     steps:
       - script: |
-          sudo apt-get install build-essential curl cmake
+          sudo apt-get install build-essential curl cmake llvm lld
         displayName: Install system packages
       - script: |
           curl https://get.wasmer.io -sSfL | sh
         displayName: Install wasmer
       - script: |
-          curl -sL -o - https://github.com/WebAssembly/wasi-sdk/releases/download/wasi-sdk-12/wasi-sdk-12.0-linux.tar.gz | tar xz -f - -C /opt/
-          sudo mv /opt/wasi-sdk-* /opt/wasi-sdk
-          sudo ln -s /opt/wasi-sdk/share/*sysroot* /opt/wasi-sysroot
-        displayName: Install the WASI SDK
+          curl -sL -o - https://ziglang.org/download/0.8.0/zig-linux-x86_64-0.8.0.tar.xz | tar xJ -f - -C /opt/
+          sudo mv /opt/zig-* /opt/zig
+          env PATH=/opt/zig/bin:/opt/zig:$PATH
+        displayName: Install the Zig SDK
       - script: |
           env WASMER_DIR=${HOME}/.wasmer PATH=${HOME}/.wasmer/bin:/opt/wasi-sdk/bin:${HOME}/.cargo/bin:$PATH dist-build/wasm32-wasi.sh
         displayName: Compile libsodium
diff --git a/configure.ac b/configure.ac
index 124366c1..993662e1 100644
--- a/configure.ac
+++ b/configure.ac
@@ -818,7 +818,9 @@ dnl Checks for functions and headers
 AC_FUNC_ALLOCA
 AS_IF([test "x$EMSCRIPTEN" = "x"],[
   AC_CHECK_FUNCS([arc4random arc4random_buf])
-  AC_CHECK_FUNCS([mmap mlock madvise mprotect])
+  AS_IF([test "x$WASI" = "x"],[
+    AC_CHECK_FUNCS([mmap mlock madvise mprotect])
+  ])
 
   AC_MSG_CHECKING(for getrandom with a standard API)
   AC_LINK_IFELSE([AC_LANG_PROGRAM([[
@@ -867,7 +869,10 @@ AS_IF([test "x$WASI" = "x"],[
 ])
 
 AC_CHECK_FUNCS([posix_memalign nanosleep])
-AC_CHECK_FUNCS([memset_s explicit_bzero explicit_memset])
+
+AS_IF([test "x$WASI" = "x"],[
+  AC_CHECK_FUNCS([memset_s explicit_bzero explicit_memset])
+])
 
 AC_SUBST([LIBTOOL_EXTRA_FLAGS])
 
diff --git a/dist-build/wasm32-wasi.sh b/dist-build/wasm32-wasi.sh
index 4142a99f..36d39dfa 100755
--- a/dist-build/wasm32-wasi.sh
+++ b/dist-build/wasm32-wasi.sh
@@ -1,37 +1,20 @@
 #! /bin/sh
 
-if [ -z "$WASI_LIBC" ]; then
-  for path in /opt/wasi-libc /opt/wasi-sysroot; do
-    if [ -d "$path" ]; then
-      export WASI_LIBC="$path"
-      break
-    fi
-  done
-fi
-if [ -z "$WASI_LIBC" ]; then
-  echo "Set WASI_LIBC to the path to the WASI libc sysroot" >&2
-  exit 1
-fi
-
-export PATH="/usr/local/opt/llvm/bin:$PATH"
+export PATH="/opt/zig/bin:/opt/zig:/usr/local/opt/llvm/bin:$PATH"
 
 export PREFIX="$(pwd)/libsodium-wasm32-wasi"
 
 mkdir -p $PREFIX || exit 1
 
-export CC="clang"
-export CFLAGS="-DED25519_NONDETERMINISTIC=1 --target=wasm32-wasi --sysroot=${WASI_LIBC} -O2"
+export CC="zig cc"
+export CFLAGS="-DED25519_NONDETERMINISTIC=1 --target=wasm32-wasi -O2"
 export LDFLAGS="-s -Wl,--stack-first"
-export NM="llvm-nm"
-export AR="llvm-ar"
-export RANLIB="llvm-ranlib"
+export AR="zig ar"
+export RANLIB="zig ranlib"
 export STRIP="llvm-strip"
 
 make distclean >/dev/null
 
-grep -q -F -- 'wasi' build-aux/config.sub ||
-  sed -i -e 's/-nacl\*)/-nacl*|-wasi)/' build-aux/config.sub
-
 if [ "x$1" = "x--bench" ]; then
   export BENCHMARKS=1
   export CPPFLAGS="-DBENCHMARKS -DITERATIONS=100"
@@ -43,10 +26,13 @@ else
   export LIBSODIUM_ENABLE_MINIMAL_FLAG=""
 fi
 
-./configure ${LIBSODIUM_ENABLE_MINIMAL_FLAG} \
-  --prefix="$PREFIX" --with-sysroot="$WASI_LIBC" \
+if ! ./configure ${LIBSODIUM_ENABLE_MINIMAL_FLAG} \
+  --prefix="$PREFIX" \
   --host=wasm32-wasi \
-  --disable-ssp --disable-shared || exit 1
+  --disable-ssp --disable-shared --without-pthreads; then
+  cat config.log
+  exit 1
+fi
 
 NPROCESSORS=$(getconf NPROCESSORS_ONLN 2>/dev/null || getconf _NPROCESSORS_ONLN 2>/dev/null)
 PROCESSORS=${NPROCESSORS:-3}