diff --git a/RELEASENOTES.md b/RELEASENOTES.md
index 3da7d77..1d260b4 100644
--- a/RELEASENOTES.md
+++ b/RELEASENOTES.md
@@ -14,5 +14,6 @@
 - Added support for compiling Typst documents with multiple PDF standards simultaneously (e.g. `v-1.7`, `a-2b`, etc.) by exposing a `pdfStandards` parameter in the `TypstCompiler.Compile` API, leveraging the underlying `typst-pdf` crate updates in Typst 0.15.
 
 ### Changed
+- `sysInputs` parameters on `TypstCompiler` and the `SetSysInputs` argument are now `IDictionary<string, string>` instead of `Dictionary<string, string>`, so a `ReadOnlyDictionary<string, string>`, `ImmutableDictionary<string, string>` or any other implementation can be passed. Existing calls that pass a `Dictionary<string, string>` are unaffected.
 - `compiler.CompilePdf(Stream)`, `compiler.CompilePdfAsync(Stream)`, `compiler.CompilePdf(string outputFile)` and `compiler.CompilePdfAsync(string outputFile)` now stream the document straight from native memory to the destination and return the compiler warnings, rather than returning a `PdfResult` that had to be materialised on the managed heap first. Use `compiler.CompilePdf()` when you want the bytes.
 - `compiler.Compile(outputFile, format)` and `compiler.CompileSvg(...)` no longer copy the rendered output onto the managed heap before writing or decoding it.
diff --git a/src/typstsharp.tests/Tests.cs b/src/typstsharp.tests/Tests.cs
index 475e46c..47e653a 100644
--- a/src/typstsharp.tests/Tests.cs
+++ b/src/typstsharp.tests/Tests.cs
@@ -1,3 +1,4 @@
+using System.Collections.ObjectModel;
 using System.Text;
 using UglyToad.PdfPig;
 using UglyToad.PdfPig.Content;
@@ -244,6 +245,28 @@ public async Task ErrorWithNullByteIsHandledCorrectly()
         await Assert.That(ex!.Message).Contains("foo\0bar");
     }
 
+    [Test]
+    public async Task SysInputsParameterAcceptsReadOnlyDictionary()
+    {
+        var sysInputs = new ReadOnlyDictionary<string, string>(
+            new Dictionary<string, string> { ["greeting"] = "Hello Inputs" });
+
+        using var compiler = TypstCompiler.FromSource("#sys.inputs.greeting", sysInputs: sysInputs);
+        var plainText = GetPlainText(compiler.CompilePdf());
+        await Assert.That(plainText).Contains("Hello Inputs");
+    }
+
+    [Test]
+    public async Task SetSysInputsAcceptsReadOnlyDictionary()
+    {
+        using var compiler = TypstCompiler.FromSource("#sys.inputs.greeting");
+        compiler.SetSysInputs(new ReadOnlyDictionary<string, string>(
+            new Dictionary<string, string> { ["greeting"] = "Hello Later" }));
+
+        var plainText = GetPlainText(compiler.CompilePdf());
+        await Assert.That(plainText).Contains("Hello Later");
+    }
+
     [Test]
     public async Task SourceAfterNullByteIsNotTruncated()
     {
diff --git a/src/typstsharp/JsonSerialisation.cs b/src/typstsharp/JsonSerialisation.cs
index 1decda4..5605cf5 100644
--- a/src/typstsharp/JsonSerialisation.cs
+++ b/src/typstsharp/JsonSerialisation.cs
@@ -8,5 +8,5 @@
 namespace typstsharp;
 
 [JsonSourceGenerationOptions(WriteIndented = true)]
-[JsonSerializable(typeof(Dictionary<string, string>))]
+[JsonSerializable(typeof(IDictionary<string, string>))]
 internal partial class SourceGenerationContext : JsonSerializerContext { }
\ No newline at end of file
diff --git a/src/typstsharp/TypstCompiler.cs b/src/typstsharp/TypstCompiler.cs
index bbf1b22..079f319 100644
--- a/src/typstsharp/TypstCompiler.cs
+++ b/src/typstsharp/TypstCompiler.cs
@@ -34,7 +34,7 @@ public class TypstCompiler : IDisposable
     /// that directory, which keeps compilation off the network.
     /// </param>
     /// <exception cref="Exception">Thrown when the Typst compiler fails to initialize.</exception>
-    public TypstCompiler(string inputPath, Fonts? fonts = null, Dictionary<string, string>? sysInputs = null, string? root = null, string? packagePath = null, bool includeSystemPackages = true)
+    public TypstCompiler(string inputPath, Fonts? fonts = null, IDictionary<string, string>? sysInputs = null, string? root = null, string? packagePath = null, bool includeSystemPackages = true)
         : this(inputPath, null, fonts, sysInputs, root, packagePath, includeSystemPackages)
     {
     }
@@ -53,7 +53,7 @@ public TypstCompiler(string inputPath, Fonts? fonts = null, Dictionary<string, s
     /// that directory, which keeps compilation off the network.
     /// </param>
     /// <returns>A new <see cref="TypstCompiler"/> instance.</returns>
-    public static TypstCompiler FromSource(string source, Fonts? fonts = null, Dictionary<string, string>? sysInputs = null, string? root = null, string? packagePath = null, bool includeSystemPackages = true)
+    public static TypstCompiler FromSource(string source, Fonts? fonts = null, IDictionary<string, string>? sysInputs = null, string? root = null, string? packagePath = null, bool includeSystemPackages = true)
     {
         return new TypstCompiler(null, source, fonts, sysInputs, root, packagePath, includeSystemPackages);
     }
@@ -72,7 +72,7 @@ public static TypstCompiler FromSource(string source, Fonts? fonts = null, Dicti
     /// that directory, which keeps compilation off the network.
     /// </param>
     /// <returns>A new <see cref="TypstCompiler"/> instance.</returns>
-    public static TypstCompiler FromFile(string path, Fonts? fonts = null, Dictionary<string, string>? sysInputs = null, string? root = null, string? packagePath = null, bool includeSystemPackages = true)
+    public static TypstCompiler FromFile(string path, Fonts? fonts = null, IDictionary<string, string>? sysInputs = null, string? root = null, string? packagePath = null, bool includeSystemPackages = true)
     {
         return new TypstCompiler(path, null, fonts, sysInputs, root, packagePath, includeSystemPackages);
     }
@@ -91,7 +91,7 @@ public static TypstCompiler FromFile(string path, Fonts? fonts = null, Dictionar
     public static PdfResult CompilePdf(
         string source,
         Fonts? fonts = null,
-        Dictionary<string, string>? sysInputs = null,
+        IDictionary<string, string>? sysInputs = null,
         string? root = null,
         string? packagePath = null,
         bool includeSystemPackages = true,
@@ -115,7 +115,7 @@ public static PdfResult CompilePdf(
     public static PdfResult CompilePdfFromFile(
         string path,
         Fonts? fonts = null,
-        Dictionary<string, string>? sysInputs = null,
+        IDictionary<string, string>? sysInputs = null,
         string? root = null,
         string? packagePath = null,
         bool includeSystemPackages = true,
@@ -140,7 +140,7 @@ public static SvgResult CompileSvg(
         string source,
         float ppi = 144.0f,
         Fonts? fonts = null,
-        Dictionary<string, string>? sysInputs = null,
+        IDictionary<string, string>? sysInputs = null,
         string? root = null,
         string? packagePath = null,
         bool includeSystemPackages = true)
@@ -164,7 +164,7 @@ public static SvgResult CompileSvgFromFile(
         string path,
         float ppi = 144.0f,
         Fonts? fonts = null,
-        Dictionary<string, string>? sysInputs = null,
+        IDictionary<string, string>? sysInputs = null,
         string? root = null,
         string? packagePath = null,
         bool includeSystemPackages = true)
@@ -188,7 +188,7 @@ public static PngResult CompilePng(
         string source,
         float ppi = 144.0f,
         Fonts? fonts = null,
-        Dictionary<string, string>? sysInputs = null,
+        IDictionary<string, string>? sysInputs = null,
         string? root = null,
         string? packagePath = null,
         bool includeSystemPackages = true)
@@ -212,7 +212,7 @@ public static PngResult CompilePngFromFile(
         string path,
         float ppi = 144.0f,
         Fonts? fonts = null,
-        Dictionary<string, string>? sysInputs = null,
+        IDictionary<string, string>? sysInputs = null,
         string? root = null,
         string? packagePath = null,
         bool includeSystemPackages = true)
@@ -223,7 +223,7 @@ public static PngResult CompilePngFromFile(
 
     
 
-    private unsafe TypstCompiler(string? inputPath, string? inputSource, Fonts? fonts, Dictionary<string, string>? sysInputs, string? root, string? packagePath = null, bool includeSystemPackages = true)
+    private unsafe TypstCompiler(string? inputPath, string? inputSource, Fonts? fonts, IDictionary<string, string>? sysInputs, string? root, string? packagePath = null, bool includeSystemPackages = true)
     {
         fonts ??= new Fonts();
         var fontPaths = fonts.FontPaths ?? [];
@@ -267,7 +267,7 @@ private unsafe TypstCompiler(string? inputPath, string? inputSource, Fonts? font
 
         var packagePathPtr = packagePath != null ? Marshal.StringToCoTaskMemUTF8(packagePath) : IntPtr.Zero;
 
-        var sysInputsJson = sysInputs == null ? "{}" : JsonSerializer.Serialize<Dictionary<string, string>>(sysInputs, sourceGenOptions);
+        var sysInputsJson = sysInputs == null ? "{}" : JsonSerializer.Serialize<IDictionary<string, string>>(sysInputs, sourceGenOptions);
         var sysInputsPtr = Marshal.StringToCoTaskMemUTF8(sysInputsJson);
 
         try
@@ -548,11 +548,11 @@ public void Compile(string outputFile, string format, float ppi = 144.0f, IEnume
     /// </summary>
     /// <param name="inputs">A dictionary of key-value pairs. Values are serialized to JSON and passed to the compiler.</param>
     /// <exception cref="Exception">Thrown if the inputs fail to be set in the native compiler.</exception>
-    public unsafe void SetSysInputs(Dictionary<string, string> inputs)
+    public unsafe void SetSysInputs(IDictionary<string, string> inputs)
     {
         if (_disposed) throw new ObjectDisposedException(nameof(TypstCompiler));
 
-        var sysInputsJson = JsonSerializer.Serialize<Dictionary<string, string>>(inputs, sourceGenOptions);
+        var sysInputsJson = JsonSerializer.Serialize<IDictionary<string, string>>(inputs, sourceGenOptions);
         var sysInputsPtr = Marshal.StringToCoTaskMemUTF8(sysInputsJson);
         try
         {