diff --git a/crates/scriptcheck/src/lex.rs b/crates/scriptcheck/src/lex.rs
index 02d8c2de0..a9a805d87 100644
--- a/crates/scriptcheck/src/lex.rs
+++ b/crates/scriptcheck/src/lex.rs
@@ -457,10 +457,20 @@ impl<'s> Lexer<'s> {
 
     /// A line that starts with `#` and then `rest` is a private name here, not a preprocessor line:
     /// the line is inside braces or in the code of an XML literal, and the name `rest` starts with
-    /// is not a directive's.
+    /// is not a directive's. The name runs over every character a name may hold, written out or as
+    /// an escape, so `#include$size` is not `#include`.
     pub fn private_line(&self, rest: &str) -> bool {
         let in_code = !self.braces.is_empty() || self.deeper_braces > 0 || !self.xml.is_empty();
-        let end = rest.find(|c: char| !c.is_ascii_alphanumeric() && c != '_').unwrap_or(rest.len());
+        let mut end = 0;
+        while let Some(more) = rest.get(end..) {
+            let len = match more.chars().next() {
+                Some('\\') => escape(more).filter(|&(c, _)| ident_part(c)).map(|(_, len)| len),
+                Some(c) if ident_part(c) => Some(c.len_utf8()),
+                _ => None,
+            };
+            let Some(len) = len else { break };
+            end += len;
+        }
         let name = rest.get(..end).unwrap_or_default();
         in_code && !catalog::DIRECTIVES.iter().any(|d| d.eq_ignore_ascii_case(name))
     }
diff --git a/crates/scriptcheck/src/tests.rs b/crates/scriptcheck/src/tests.rs
index 19cee6160..853f212c1 100644
--- a/crates/scriptcheck/src/tests.rs
+++ b/crates/scriptcheck/src/tests.rs
@@ -491,6 +491,21 @@ fn private_name_at_line_start_is_not_a_directive() {
     );
 }
 
+#[test]
+fn private_name_that_starts_with_a_directive_name_is_not_a_directive() {
+    let r = report(concat!(
+        "class Box {\n",
+        "  #include$size = 1;\n",
+        "  #include\u{e9} = 2;\n",
+        "  #include\\u0041 = 3;\n",
+        "  #include\\u{41} = 4;\n",
+        "  #INCLUDE 'a.jsxinc'\n",
+        "}\n",
+    ));
+    let directives: Vec<_> = r.directives.iter().map(|d| (d.name, d.line)).collect();
+    assert_eq!(directives, [("include", 6)]);
+}
+
 #[test]
 fn xml_code_uses_escaped_names() {
     let r = report("var x = <a>{\\u{61}pp.activeDocument}</a>;\nvar y = <b>\\u0061pp.z \\u{61}</b>;\n");