diff --git a/src/uu/expr/src/syntax_tree.rs b/src/uu/expr/src/syntax_tree.rs
index 0950020c9..d41ef90e2 100644
--- a/src/uu/expr/src/syntax_tree.rs
+++ b/src/uu/expr/src/syntax_tree.rs
@@ -685,9 +685,9 @@ impl<'a, S: AsRef<str>> Parser<'a, S> {
                 }
             }
             "substr" => {
-                let string = self.parse_expression()?;
-                let pos = self.parse_expression()?;
-                let length = self.parse_expression()?;
+                let string = self.parse_simple_expression()?;
+                let pos = self.parse_simple_expression()?;
+                let length = self.parse_simple_expression()?;
                 AstNodeInner::Substr {
                     string: Box::new(string),
                     pos: Box::new(pos),
diff --git a/tests/by-util/test_expr.rs b/tests/by-util/test_expr.rs
index 0a16d4ea9..fdf68ed73 100644
--- a/tests/by-util/test_expr.rs
+++ b/tests/by-util/test_expr.rs
@@ -507,6 +507,19 @@ fn test_substr() {
         .stderr_only("expr: syntax error: unexpected argument 'substr'\n");
 }
 
+#[test]
+fn test_substr_precedence() {
+    new_ucmd!()
+        .args(&["substr", "ab cd", "3", "1", "!=", " "])
+        .fails_with_code(1)
+        .stdout_only("0\n");
+
+    new_ucmd!()
+        .args(&["substr", "ab cd", "2", "1", "!=", " "])
+        .succeeds()
+        .stdout_only("1\n");
+}
+
 #[test]
 fn test_invalid_substr() {
     new_ucmd!()