diff --git a/src/lib.rs b/src/lib.rs
index 680ea7c..6589e89 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -955,7 +955,7 @@ impl Parser {
                         if let Ok(val) = tokens[idx + 4].parse::<i32>() {
                             ymd.append(val, &tokens[idx + 4], None)?;
                         } else {
-                            return Err(ParseInternalError::ValueError("".to_owned()));
+                            return Err(ParseInternalError::ValueError("Unknown string format".to_owned()));
                         }
                     }
 
diff --git a/src/tests/fuzzing.rs b/src/tests/fuzzing.rs
index 2508f02..e204d17 100644
--- a/src/tests/fuzzing.rs
+++ b/src/tests/fuzzing.rs
@@ -12,7 +12,9 @@ fn test_fuzz() {
     assert_eq!(parse("\x2D\x38\x31\x39\x34\x38\x34"), Err(ParseError::InvalidMonth));
     // Garbage in the third delimited field
     assert_eq!(parse("2..\x00\x000d\x00+\x010d\x01\x00\x00\x00+"),
-               Err(ParseError::InternalError(ParseInternalError::ValueError("".to_owned()))));
+               Err(ParseError::InternalError(ParseInternalError::ValueError("Unknown string format".to_owned()))));
+    // OverflowError: Python int too large to convert to C long
+    // assert_eq!(parse("8888884444444888444444444881"), Err(ParseError::AmPmWithoutHour));
     let default = NaiveDate::from_ymd(2016, 6, 29).and_hms(0, 0, 0);
     let mut p = Parser::default();
     let res = p.parse("\x0D\x31", None, None, false, false, Some(&default), false, HashMap::new()).unwrap();