diff --git a/src/lib.rs b/src/lib.rs
index 2e3cd93..b2f926e 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -247,6 +247,10 @@ impl CondUnit {
         (CondUnit::Star, ONE_SECOND_NANOSECOND)
     }
 
+    fn contain(c: char) -> bool {
+        Self::expect_val().contains(&&*c.to_string())
+    }
+
     fn change_duration(&self) -> u64 {
         match self {
             CondUnit::Plus => 0,
diff --git a/src/unit.rs b/src/unit.rs
index 4546655..e74a77b 100644
--- a/src/unit.rs
+++ b/src/unit.rs
@@ -1,6 +1,6 @@
 use crate::error::PError;
 use crate::{
-    DError, DResult, ExpectErr, ONE_DAY_NANOSECOND, ONE_HOUR_NANOSECOND,
+    CondUnit, DError, DResult, ExpectErr, ONE_DAY_NANOSECOND, ONE_HOUR_NANOSECOND,
     ONE_MICROSECOND_NANOSECOND, ONE_MILLISECOND_NANOSECOND, ONE_MINUTE_NANOSECOND,
     ONE_MONTH_NANOSECOND, ONE_SECOND_NANOSECOND, ONE_WEEK_NANOSECOND, ONE_YEAR_NANOSECOND,
 };
@@ -112,7 +112,7 @@ pub(crate) fn opt_unit_abbr<'a>(input: &mut &'a str) -> PResult<TimeUnit, PError
             return Ok(TimeUnit::default());
         }
 
-        if peek((multispace, one_of(|c| c == '+' || c == '*')))
+        if peek((multispace, one_of(CondUnit::contain)))
             .parse_next(input)
             .is_ok()
         {