diff --git a/ci/aarch64-linux-debug.sh b/ci/aarch64-linux-debug.sh
index 94f40c557b..90ed8bbc35 100644
--- a/ci/aarch64-linux-debug.sh
+++ b/ci/aarch64-linux-debug.sh
@@ -60,6 +60,7 @@ stage3-debug/bin/zig build -Dtarget=arm-linux-musleabihf
 # TODO: add -fqemu back to this line
 
 stage3-debug/bin/zig build test docs \
+  -j1 \
   -fwasmtime \
   -Dstatic-llvm \
   -Dtarget=native-native-musl \
diff --git a/ci/aarch64-linux-release.sh b/ci/aarch64-linux-release.sh
index 65d6063f25..e99e3e1c08 100644
--- a/ci/aarch64-linux-release.sh
+++ b/ci/aarch64-linux-release.sh
@@ -60,6 +60,7 @@ stage3-release/bin/zig build -Dtarget=arm-linux-musleabihf
 # TODO: add -fqemu back to this line
 
 stage3-release/bin/zig build test docs \
+  -j1 \
   -fwasmtime \
   -Dstatic-llvm \
   -Dtarget=native-native-musl \
diff --git a/ci/aarch64-macos.sh b/ci/aarch64-macos.sh
index b4533e149f..634a60b600 100755
--- a/ci/aarch64-macos.sh
+++ b/ci/aarch64-macos.sh
@@ -44,6 +44,7 @@ PATH="$HOME/local/bin:$PATH" cmake .. \
 $HOME/local/bin/ninja install
 
 stage3-release/bin/zig build test docs \
+  -j1 \
   --zig-lib-dir "$(pwd)/../lib" \
   -Denable-macos-sdk \
   -Dstatic-llvm \
diff --git a/ci/x86_64-linux-debug.sh b/ci/x86_64-linux-debug.sh
index 7f2382f04a..1267a2d753 100755
--- a/ci/x86_64-linux-debug.sh
+++ b/ci/x86_64-linux-debug.sh
@@ -58,6 +58,7 @@ stage3-debug/bin/zig fmt --check .. \
 stage3-debug/bin/zig build -Dtarget=arm-linux-musleabihf
 
 stage3-debug/bin/zig build test docs \
+  -j1 \
   -fqemu \
   -fwasmtime \
   -Dstatic-llvm \
diff --git a/ci/x86_64-linux-release.sh b/ci/x86_64-linux-release.sh
index cdb24e4a6f..3305f5e951 100755
--- a/ci/x86_64-linux-release.sh
+++ b/ci/x86_64-linux-release.sh
@@ -59,6 +59,7 @@ stage3-release/bin/zig fmt --check .. \
 stage3-release/bin/zig build -Dtarget=arm-linux-musleabihf
 
 stage3-release/bin/zig build test docs \
+  -j1 \
   -fqemu \
   -fwasmtime \
   -Dstatic-llvm \
diff --git a/ci/x86_64-macos-debug.sh b/ci/x86_64-macos-debug.sh
index c24ff5d295..edd35970b8 100755
--- a/ci/x86_64-macos-debug.sh
+++ b/ci/x86_64-macos-debug.sh
@@ -48,6 +48,7 @@ cmake .. \
 make $JOBS install
 
 stage3/bin/zig build test docs \
+  -j1 \
   --zig-lib-dir "$(pwd)/../lib" \
   -Denable-macos-sdk \
   -Dstatic-llvm \
diff --git a/ci/x86_64-macos-release.sh b/ci/x86_64-macos-release.sh
index a4dedb4446..65dea3afcb 100755
--- a/ci/x86_64-macos-release.sh
+++ b/ci/x86_64-macos-release.sh
@@ -48,6 +48,7 @@ cmake .. \
 make $JOBS install
 
 stage3/bin/zig build test docs \
+  -j1 \
   --zig-lib-dir "$(pwd)/../lib" \
   -Denable-macos-sdk \
   -Dstatic-llvm \
diff --git a/test/tests.zig b/test/tests.zig
index e470a4f251..fe2efbc06e 100644
--- a/test/tests.zig
+++ b/test/tests.zig
@@ -1067,6 +1067,10 @@ pub const StandaloneContext = struct {
         zig_args.append(rel_zig_exe) catch unreachable;
         zig_args.append("build") catch unreachable;
 
+        // TODO: fix the various non-concurrency-safe issues in zig's standalone tests,
+        // and then remove this!
+        zig_args.append("-j1") catch @panic("OOM");
+
         zig_args.append("--build-file") catch unreachable;
         zig_args.append(b.pathFromRoot(build_file)) catch unreachable;