diff --git a/.github/workflows/issue236-windows.yml b/.github/workflows/issue236-windows.yml
new file mode 100644
index 0000000..700a1db
--- /dev/null
+++ b/.github/workflows/issue236-windows.yml
@@ -0,0 +1,200 @@
+name: Issue 236 Windows diagnostics
+
+on:
+  pull_request:
+    paths:
+      - ".github/workflows/issue236-windows.yml"
+      - "test/issue236_windows.jl"
+      - "src/**"
+      - "Project.toml"
+  workflow_dispatch:
+
+jobs:
+  build-yggdrasil-variant:
+    name: Build Yggdrasil variant / ${{ matrix.variant }}
+    if: github.event_name == 'workflow_dispatch'
+    runs-on: ubuntu-latest
+    timeout-minutes: 60
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - variant: fno-strict-aliasing
+            cflags: -fno-strict-aliasing
+          - variant: fno-tree-vectorize
+            cflags: -fno-tree-vectorize
+    steps:
+      - uses: julia-actions/setup-julia@v2
+        with:
+          version: "1.12"
+
+      - uses: actions/checkout@v5
+        with:
+          repository: JuliaPackaging/Yggdrasil
+          path: Yggdrasil
+
+      - name: Patch MariaDB Connector/C recipe
+        shell: bash
+        run: |
+          set -euo pipefail
+          cd Yggdrasil/M/MariaDB_Connector_C
+          perl -0pi -e 's/\Q-Wno-error -Wno-incompatible-pointer-types\E/-Wno-error -Wno-incompatible-pointer-types $ENV{EXTRA_CFLAGS}/' build_tarballs.jl
+          grep -n -- "$EXTRA_CFLAGS" build_tarballs.jl
+        env:
+          EXTRA_CFLAGS: ${{ matrix.cflags }}
+
+      - name: Build Windows tarball
+        shell: bash
+        run: |
+          set -euo pipefail
+          cd Yggdrasil/M/MariaDB_Connector_C
+          julia --project=../.. --startup-file=no -e 'using Pkg; Pkg.instantiate()'
+          julia --project=../.. --startup-file=no build_tarballs.jl --verbose x86_64-w64-mingw32
+          mkdir -p "$GITHUB_WORKSPACE/variant"
+          cp products/MariaDB_Connector_C.v*.x86_64-w64-mingw32.tar.gz "$GITHUB_WORKSPACE/variant/"
+          cp products/MariaDB_Connector_C-logs.v*.x86_64-w64-mingw32.tar.gz "$GITHUB_WORKSPACE/variant/"
+
+      - uses: actions/upload-artifact@v5
+        with:
+          name: mariadb-connector-c-${{ matrix.variant }}
+          path: variant/*.tar.gz
+
+  issue236:
+    name: Windows ${{ matrix.os }} / ${{ matrix.connector }}
+    runs-on: ${{ matrix.os }}
+    timeout-minutes: 30
+    strategy:
+      fail-fast: false
+      matrix:
+        os:
+          - windows-2022
+          - windows-2025
+        connector:
+          - jll-default
+          - jll-3.3.9
+          - official-3.4.9
+
+    steps:
+      - uses: actions/checkout@v5
+
+      - uses: julia-actions/setup-julia@v2
+        with:
+          version: "1"
+          arch: x64
+
+      - name: Start MySQL
+        id: setup-mysql
+        uses: shogo82148/actions-setup-mysql@v1.51.0
+        with:
+          mysql-version: "8.4"
+          root-password: root
+
+      - name: Download official Connector/C
+        if: matrix.connector == 'official-3.4.9'
+        shell: pwsh
+        run: |
+          $msi = Join-Path $env:RUNNER_TEMP "mariadb-connector-c-3.4.9-win64.msi"
+          $target = Join-Path $env:RUNNER_TEMP "mariadb-connector-c-3.4.9"
+          Invoke-WebRequest `
+            -Uri "https://dlm.mariadb.com/4751028/Connectors/c/connector-c-3.4.9/mariadb-connector-c-3.4.9-win64.msi" `
+            -OutFile $msi
+          Start-Process msiexec.exe -Wait -ArgumentList @("/a", $msi, "/qn", "TARGETDIR=$target")
+
+          $dll = Get-ChildItem $target -Recurse -Filter libmariadb.dll | Select-Object -First 1
+          if ($null -eq $dll) {
+            throw "Could not find libmariadb.dll under $target"
+          }
+
+          $plugin = Get-ChildItem $target -Recurse -Directory |
+            Where-Object { Test-Path (Join-Path $_.FullName "caching_sha2_password.dll") } |
+            Select-Object -First 1
+          if ($null -eq $plugin) {
+            throw "Could not find Connector/C plugin directory under $target"
+          }
+
+          "MYSQLJL_LIBMARIADB_OVERRIDE=$($dll.FullName)" >> $env:GITHUB_ENV
+          "MYSQLJL_PLUGIN_DIR_OVERRIDE=$($plugin.FullName)" >> $env:GITHUB_ENV
+          "$($dll.DirectoryName)" >> $env:GITHUB_PATH
+
+      - name: Run issue 236 diagnostic
+        shell: pwsh
+        env:
+          MYSQLJL_HOST: 127.0.0.1
+          MYSQLJL_PORT: "3306"
+          MYSQLJL_USER: root
+          MYSQLJL_PASSWORD: root
+          MYSQLJL_CONNECTOR: ${{ matrix.connector }}
+          MYSQLJL_JLL_VERSION: ${{ matrix.connector == 'jll-3.3.9' && '3.3.9' || 'default' }}
+        run: julia --startup-file=no test/issue236_windows.jl
+
+  issue236-yggdrasil-variant:
+    name: Windows ${{ matrix.os }} / yggdrasil-${{ matrix.variant }}
+    if: github.event_name == 'workflow_dispatch'
+    needs: build-yggdrasil-variant
+    runs-on: ${{ matrix.os }}
+    timeout-minutes: 30
+    strategy:
+      fail-fast: false
+      matrix:
+        os:
+          - windows-2022
+          - windows-2025
+        variant:
+          - fno-strict-aliasing
+          - fno-tree-vectorize
+
+    steps:
+      - uses: actions/checkout@v5
+
+      - uses: julia-actions/setup-julia@v2
+        with:
+          version: "1"
+          arch: x64
+
+      - name: Start MySQL
+        uses: shogo82148/actions-setup-mysql@v1.51.0
+        with:
+          mysql-version: "8.4"
+          root-password: root
+
+      - uses: actions/download-artifact@v5
+        with:
+          name: mariadb-connector-c-${{ matrix.variant }}
+          path: ${{ runner.temp }}/variant
+
+      - name: Use Yggdrasil variant
+        shell: pwsh
+        run: |
+          $target = Join-Path $env:RUNNER_TEMP "mariadb-connector-c-${env:MYSQLJL_CONNECTOR_VARIANT}"
+          New-Item -ItemType Directory -Force -Path $target | Out-Null
+          $tarball = Get-ChildItem (Join-Path $env:RUNNER_TEMP "variant") -Filter "MariaDB_Connector_C.v*.x86_64-w64-mingw32.tar.gz" | Select-Object -First 1
+          if ($null -eq $tarball) {
+            throw "Could not find built Connector/C tarball"
+          }
+          tar -xzf $tarball.FullName -C $target
+
+          $dll = Join-Path $target "bin/libmariadb.dll"
+          $plugin = Join-Path $target "lib/mariadb/plugin"
+          if (!(Test-Path $dll)) {
+            throw "Could not find libmariadb.dll at $dll"
+          }
+          if (!(Test-Path (Join-Path $plugin "caching_sha2_password.dll"))) {
+            throw "Could not find Connector/C plugin directory at $plugin"
+          }
+
+          "MYSQLJL_LIBMARIADB_OVERRIDE=$dll" >> $env:GITHUB_ENV
+          "MYSQLJL_PLUGIN_DIR_OVERRIDE=$plugin" >> $env:GITHUB_ENV
+          "$(Split-Path -Parent $dll)" >> $env:GITHUB_PATH
+        env:
+          MYSQLJL_CONNECTOR_VARIANT: ${{ matrix.variant }}
+
+      - name: Run issue 236 diagnostic
+        shell: pwsh
+        env:
+          MYSQLJL_HOST: 127.0.0.1
+          MYSQLJL_PORT: "3306"
+          MYSQLJL_USER: root
+          MYSQLJL_PASSWORD: root
+          MYSQLJL_CONNECTOR: yggdrasil-${{ matrix.variant }}
+          MYSQLJL_JLL_VERSION: default
+        run: julia --startup-file=no test/issue236_windows.jl
diff --git a/src/api/API.jl b/src/api/API.jl
index b0b2a60..1910488 100644
--- a/src/api/API.jl
+++ b/src/api/API.jl
@@ -7,7 +7,7 @@ export DateAndTime
 using MariaDB_Connector_C_jll
 using OpenSSL_jll: libssl, libcrypto
 
-const PLUGIN_DIR = joinpath(MariaDB_Connector_C_jll.artifact_dir, "lib", "mariadb", "plugin")
+const PLUGIN_DIR = get(ENV, "MYSQLJL_PLUGIN_DIR_OVERRIDE", joinpath(MariaDB_Connector_C_jll.artifact_dir, "lib", "mariadb", "plugin"))
 
 # Pre-load OpenSSL libraries so they're available when MariaDB loads plugins.
 # MariaDB authentication plugins (e.g., caching_sha2_password) depend on OpenSSL,
@@ -37,4 +37,4 @@ include("capi.jl")
 # Prepared statement API functions
 include("papi.jl")
 
-end # module
\ No newline at end of file
+end # module
diff --git a/src/api/ccalls.jl b/src/api/ccalls.jl
index 95fc51c..bf4f7ef 100644
--- a/src/api/ccalls.jl
+++ b/src/api/ccalls.jl
@@ -1,11 +1,13 @@
+const libmariadb_for_ccall = get(ENV, "MYSQLJL_LIBMARIADB_OVERRIDE", libmariadb)
+
 macro c(func, ret, args, vals...)
     if Sys.iswindows()
         esc(quote
-            ret = ccall( ($func, libmariadb), stdcall, $ret, $args, $(vals...))
+            ret = ccall( ($func, libmariadb_for_ccall), stdcall, $ret, $args, $(vals...))
         end)
     else
         esc(quote
-            ret = ccall( ($func, libmariadb),          $ret, $args, $(vals...))
+            ret = ccall( ($func, libmariadb_for_ccall),          $ret, $args, $(vals...))
         end)
     end
 end
diff --git a/test/issue236_windows.jl b/test/issue236_windows.jl
new file mode 100644
index 0000000..e866387
--- /dev/null
+++ b/test/issue236_windows.jl
@@ -0,0 +1,185 @@
+if get(ENV, "MYSQLJL_BOOTSTRAPPED", "false") != "true"
+    using Pkg
+
+    jll_pkg_version(v::String) = VersionNumber(occursin("+", v) ? v : string(v, "+0"))
+
+    Pkg.activate(; temp=true)
+    Pkg.develop(PackageSpec(path=dirname(@__DIR__)))
+    Pkg.add([
+        PackageSpec(name="DBInterface"),
+        PackageSpec(name="Tables"),
+    ])
+
+    jll_version = get(ENV, "MYSQLJL_JLL_VERSION", "default")
+    if jll_version != "default"
+        Pkg.add(PackageSpec(name="MariaDB_Connector_C_jll", version=jll_pkg_version(jll_version)))
+    else
+        Pkg.add(PackageSpec(name="MariaDB_Connector_C_jll"))
+    end
+
+    Pkg.instantiate()
+    Pkg.status()
+
+    ENV["MYSQLJL_BOOTSTRAPPED"] = "true"
+    include(@__FILE__)
+    exit()
+end
+
+using DBInterface
+using Libdl
+using MariaDB_Connector_C_jll
+using MySQL
+using Random
+using Tables
+
+function logline(xs...)
+    println(xs...)
+    flush(stdout)
+    return nothing
+end
+
+function log_mysql_bind_layout()
+    names = fieldnames(MySQL.API.MYSQL_BIND)
+    logline("MYSQL_BIND_SIZE ", sizeof(MySQL.API.MYSQL_BIND))
+    for (i, name) in pairs(names)
+        logline("MYSQL_BIND_FIELD ", name, " offset=", fieldoffset(MySQL.API.MYSQL_BIND, i))
+    end
+    return nothing
+end
+
+function connect_root(; db=nothing)
+    host = get(ENV, "MYSQLJL_HOST", "127.0.0.1")
+    port = parse(Int, get(ENV, "MYSQLJL_PORT", "3306"))
+    user = get(ENV, "MYSQLJL_USER", "root")
+    password = get(ENV, "MYSQLJL_PASSWORD", "root")
+
+    if db === nothing
+        return DBInterface.connect(MySQL.Connection, host, user, password; port=port, connect_timeout=10)
+    else
+        return DBInterface.connect(MySQL.Connection, host, user, password; db=db, port=port, connect_timeout=10)
+    end
+end
+
+function wait_for_connection(; db=nothing, timeout=30.0)
+    start = time()
+    last_err = nothing
+    while time() - start < timeout
+        try
+            return connect_root(; db=db)
+        catch err
+            last_err = err
+            logline("WAIT_CONNECTION db=", db, " error=", sprint(showerror, err))
+            sleep(1)
+        end
+    end
+    error("MySQL did not become ready: ", sprint(showerror, last_err))
+end
+
+function placeholders(n::Integer)
+    return join(fill("?", n), ",")
+end
+
+function query_for(shape::Symbol, n::Integer)
+    marks = placeholders(n)
+    if shape === :table
+        return "SELECT id FROM myTable WHERE id IN ($marks)"
+    elseif shape === :constant
+        return "SELECT 1 AS id WHERE 1 IN ($marks)"
+    elseif shape === :echo
+        return "SELECT $marks"
+    else
+        error("unknown query shape: $shape")
+    end
+end
+
+function consume(cursor)
+    rows = 0
+    for _ in cursor
+        rows += 1
+    end
+    return rows
+end
+
+function run_case(conn, name::String, shape::Symbol, params; mysql_store_result::Bool=true)
+    n = length(params)
+    query = query_for(shape, n)
+    logline("BEGIN name=", name,
+            " shape=", shape,
+            " n=", n,
+            " eltype=", eltype(params),
+            " mysql_store_result=", mysql_store_result)
+    logline("QUERY ", query)
+    logline("FIRST_VALUES ", collect(Iterators.take(params, min(n, 5))))
+
+    stmt = DBInterface.prepare(conn, query)
+    logline("PREPARED nparams=", stmt.nparams, " nfields=", stmt.nfields)
+
+    cursor = DBInterface.execute(stmt, params; mysql_store_result=mysql_store_result)
+    rows = consume(cursor)
+    logline("DONE name=", name, " rows=", rows)
+
+    DBInterface.close!(stmt)
+    return nothing
+end
+
+function prepare_database()
+    conn = wait_for_connection()
+    try
+        version = DBInterface.execute(conn, "SELECT VERSION() AS version") |> Tables.columntable
+        logline("SERVER_VERSION ", only(version.version))
+
+        DBInterface.execute(conn, "DROP DATABASE IF EXISTS issue236")
+        DBInterface.execute(conn, "CREATE DATABASE issue236")
+    finally
+        DBInterface.close!(conn)
+    end
+
+    conn = wait_for_connection(db="issue236")
+    DBInterface.execute(conn, "CREATE TABLE myTable (id BIGINT UNSIGNED NOT NULL PRIMARY KEY)")
+
+    stmt = DBInterface.prepare(conn, "INSERT INTO myTable (id) VALUES (?)")
+    try
+        for id in UInt64(1):UInt64(512)
+            DBInterface.execute(stmt, id)
+        end
+    finally
+        DBInterface.close!(stmt)
+    end
+    return conn
+end
+
+function main()
+    logline("JULIA_VERSION ", VERSION)
+    logline("OS ", Sys.KERNEL, " MACHINE ", Sys.MACHINE)
+    logline("WORD_SIZE ", Sys.WORD_SIZE)
+    logline("CONNECTOR ", get(ENV, "MYSQLJL_CONNECTOR", "unknown"))
+    logline("JLL_LIBMARIADB ", MariaDB_Connector_C_jll.libmariadb)
+    logline("CCALL_LIBMARIADB ", MySQL.API.libmariadb_for_ccall)
+    logline("PLUGIN_DIR ", MySQL.API.PLUGIN_DIR)
+    logline("LIBMARIADB_HANDLE ", Libdl.dlopen_e(MySQL.API.libmariadb_for_ccall))
+    log_mysql_bind_layout()
+
+    conn = prepare_database()
+    try
+        Random.seed!(0x236)
+
+        for n in (31, 32, 33, 34, 64, 128)
+            run_case(conn, "table-small-uint64", :table, UInt64.(1:n))
+        end
+
+        for n in (32, 33, 34)
+            run_case(conn, "table-small-int64", :table, Int64.(1:n))
+            run_case(conn, "table-random-uint64", :table, rand(UInt64, n))
+            run_case(conn, "constant-small-uint64", :constant, UInt64.(1:n))
+            run_case(conn, "table-small-uint64-unbuffered", :table, UInt64.(1:n); mysql_store_result=false)
+        end
+
+        run_case(conn, "echo-small-uint64", :echo, UInt64.(1:33))
+    finally
+        DBInterface.close!(conn)
+    end
+
+    logline("ISSUE236_DIAGNOSTIC_COMPLETE")
+end
+
+main()