diff --git a/src/contract/mod.rs b/src/contract/mod.rs
index 823d74f..faf90bb 100644
--- a/src/contract/mod.rs
+++ b/src/contract/mod.rs
@@ -118,18 +118,9 @@ impl ContractParameters {
 
         for (outcome, payout_map) in self.outcome_payouts.iter() {
             // Check for unknown outcomes.
-            match outcome {
-                &Outcome::Attestation(outcome_index) => {
-                    if outcome_index >= self.event.outcome_messages.len() {
-                        return Err(Error);
-                    }
-                }
-                Outcome::Expiry => {
-                    if self.event.expiry.is_none() {
-                        return Err(Error);
-                    }
-                }
-            };
+            if !self.event.is_valid_outcome(outcome) {
+                return Err(Error);
+            }
 
             // Check for empty payout map.
             if payout_map.len() == 0 {
diff --git a/src/oracles.rs b/src/oracles.rs
index e0efb72..927c023 100644
--- a/src/oracles.rs
+++ b/src/oracles.rs
@@ -65,6 +65,15 @@ impl EventAnnouncement {
         Some(k + e * d)
     }
 
+    /// Returns true if the given outcome is a valid outcome to wager on
+    /// for this event.
+    pub fn is_valid_outcome(&self, outcome: &Outcome) -> bool {
+        match outcome {
+            &Outcome::Attestation(i) => i < self.outcome_messages.len(),
+            Outcome::Expiry => self.expiry.is_some(),
+        }
+    }
+
     /// Returns an iterator over all possible outcomes in the event.
     pub fn all_outcomes(&self) -> impl IntoIterator<Item = Outcome> {
         (0..self.outcome_messages.len())