diff --git a/src/lib.rs b/src/lib.rs
index 1d5cf0d..598a482 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -29,7 +29,7 @@ impl Card {
     }
     pub fn blocks_action(self, action: Action) -> bool {
         matches!((self, action),
-                 (Duke, Income) |
+                 (Duke, ForeignAid) |
                  (Captain, Steal) |
                  (Ambassador, Steal) |
                  (Contessa, Assassinate))
@@ -243,12 +243,18 @@ impl Game {
                 target: block.target,
             })),
             ResMode::Target => match agents[block.target.unwrap()].choose_block_card(&block) {
-                Some(card) => Ok(Phase::BlockChallenge(phase::BlockChallenge {
-                    blocker: block.target.unwrap(),
-                    block_card: card,
-                    action: block.action,
-                    target: block.target,
-                })),
+                Some(card) => {
+                    if card.blocks_action(block.action) {
+                        Ok(Phase::BlockChallenge(phase::BlockChallenge {
+                            blocker: block.target.unwrap(),
+                            block_card: card,
+                            action: block.action,
+                            target: block.target,
+                        }))
+                    } else {
+                        Err("Card does not block action")
+                    }
+                },
                 None => Ok(Phase::Resolution(phase::Resolution {
                     action: block.action,
                     target: block.target,
@@ -257,12 +263,16 @@ impl Game {
             ResMode::Anyone => {
                 for id in self.turn_iterator() {
                     if let Some(card) = agents[id].choose_block_card(&block) {
-                        return Ok(Phase::BlockChallenge(phase::BlockChallenge {
-                            blocker: id,
-                            block_card: card,
-                            action: block.action,
-                            target: block.target,
-                        }))
+                        if card.blocks_action(block.action) {
+                            return Ok(Phase::BlockChallenge(phase::BlockChallenge {
+                                blocker: id,
+                                block_card: card,
+                                action: block.action,
+                                target: block.target,
+                            }))
+                        } else {
+                            return Err("Card does not block action")
+                        }
                     }
                 }
                 Ok(Phase::Resolution(phase::Resolution {
@@ -512,6 +522,19 @@ mod test {
                 }))
             );
         }
+
+        // Test bad block card
+        {
+            let mut game = game.clone();
+            assert!(
+                game.block(phase::Block {
+                    action: ForeignAid,
+                    target: None,
+                }, &[&non_blocking_agent, &ambassador_block_agent, &non_blocking_agent])
+                    .is_err()
+            );
+        }
+
     }
 
     #[test]