From 2b3276fb4fa8d8c72c6b3b1136cbc84c2e2297c7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Lukas=20D=C3=BCrrenberger?= <eXpl0it3r@my-gate.net>
Date: Tue, 10 Nov 2026 12:37:59 +0100
Subject: [PATCH] Fix crash on rem lengths in text-indent and word-spacing

---
 Source/HtmlRenderer/Core/Dom/CssBoxProperties.cs      |  3 ++-
 .../Test/HtmlRenderer.Test/Css/TextPropertyTests.cs   | 11 +++++++++++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/Source/HtmlRenderer/Core/Dom/CssBoxProperties.cs b/Source/HtmlRenderer/Core/Dom/CssBoxProperties.cs
index 0167d22a4..8b1891112 100644
--- a/Source/HtmlRenderer/Core/Dom/CssBoxProperties.cs
+++ b/Source/HtmlRenderer/Core/Dom/CssBoxProperties.cs
@@ -1901,7 +1901,8 @@ public double GetEmHeight()
         protected string NoEms(string length)
         {
             var len = new CssLength(length);
-            if (len.Unit == CssUnit.Ems)
+            // CssLength reads rem as em with a parse error
+            if (len.Unit == CssUnit.Ems && !len.HasError)
             {
                 length = len.ConvertEmToPixels(GetEmHeight()).ToString();
             }
diff --git a/Source/Test/HtmlRenderer.Test/Css/TextPropertyTests.cs b/Source/Test/HtmlRenderer.Test/Css/TextPropertyTests.cs
index 53f68c3ee..eb687ef77 100644
--- a/Source/Test/HtmlRenderer.Test/Css/TextPropertyTests.cs
+++ b/Source/Test/HtmlRenderer.Test/Css/TextPropertyTests.cs
@@ -1,4 +1,5 @@
 using HtmlRenderer.Test.CssEngineSupport;
+using HtmlRenderer.Test.TestSupport;
 using TheArtOfDev.HtmlRenderer.Core.CssEngine;
 
 namespace HtmlRenderer.Test.Css;
@@ -822,4 +823,14 @@ public void OverflowWrapAlternateNameNoneIllegal()
         Assert.IsInstanceOfType<OverflowWrapProperty>(property);
         Assert.IsFalse(property.HasValue);
     }
+
+    [TestMethod]
+    [DataRow("text-indent")]
+    [DataRow("word-spacing")]
+    public void RemLengthDoesNotFailTheDocument(string property)
+    {
+        var (root, _) = LayoutHarness.Layout(LayoutHarness.Wrap($"<p id=x style='{property}: 2rem'>a b</p>"));
+
+        Assert.IsNotNull(LayoutHarness.FindById(root, "x"));
+    }
 }