diff --git a/CHANGELOG.md b/CHANGELOG.md
index dc14695211ce..7c025a94076a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -15,6 +15,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Support Leptos `class:` attributes when extracting classes ([#18093](https://github.com/tailwindlabs/tailwindcss/pull/18093))
 - Fix "Cannot read properties of undefined" crash on malformed arbitrary value ([#18133](https://github.com/tailwindlabs/tailwindcss/pull/18133))
 - Upgrade: Migrate `-mt-[0px]` to `mt-[0px]` instead of the other way around ([#18154](https://github.com/tailwindlabs/tailwindcss/pull/18154))
+- Fix Haml pre-processing crash when there is no `\n` at the end of the file ([#18155](https://github.com/tailwindlabs/tailwindcss/pull/18155))
 
 ## [4.1.7] - 2025-05-15
 
diff --git a/crates/oxide/src/extractor/pre_processors/haml.rs b/crates/oxide/src/extractor/pre_processors/haml.rs
index 810bbb2c35ed..a131618abe66 100644
--- a/crates/oxide/src/extractor/pre_processors/haml.rs
+++ b/crates/oxide/src/extractor/pre_processors/haml.rs
@@ -330,6 +330,11 @@ impl Haml {
             cursor.advance();
         }
 
+        // We didn't find a newline, we reached the end of the input
+        if last_known_newline_position == last_newline_position {
+            return cursor.pos;
+        }
+
         // Move the cursor to the last newline position
         cursor.move_to(last_newline_position);
 
@@ -446,4 +451,16 @@ mod tests {
         "#;
         Haml::test_extract_contains(input, vec!["flex", "items-center"]);
     }
+
+    // https://github.com/tailwindlabs/tailwindcss/issues/17379#issuecomment-2910108646
+    #[test]
+    fn test_crash_missing_newline() {
+        // The empty `""` will introduce a newline
+        let good = ["- index = 0", "- index += 1", ""].join("\n");
+        Haml::test_extract_contains(&good, vec!["index"]);
+
+        // This used to crash before the fix
+        let bad = ["- index = 0", "- index += 1"].join("\n");
+        Haml::test_extract_contains(&bad, vec!["index"]);
+    }
 }