diff --git a/utils/fixed_decimal/src/decimal.rs b/utils/fixed_decimal/src/decimal.rs
index 891394d9ff2..895512a3a71 100644
--- a/utils/fixed_decimal/src/decimal.rs
+++ b/utils/fixed_decimal/src/decimal.rs
@@ -2677,6 +2677,14 @@ fn test_syntax_error() {
         pub expected_err: Option<ParseError>,
     }
     let cases = [
+        TestCase {
+            input_str: "+1234567890",
+            expected_err: Some(ParseError::Syntax),
+        },
+        TestCase {
+            input_str: "-1234567890",
+            expected_err: Some(ParseError::Syntax),
+        },
         TestCase {
             input_str: "-12a34",
             expected_err: Some(ParseError::Syntax),