diff --git a/src/interpreter/mod.rs b/src/interpreter/mod.rs
index af405bda9..462d9049e 100644
--- a/src/interpreter/mod.rs
+++ b/src/interpreter/mod.rs
@@ -130,6 +130,8 @@ impl MiniscriptKey for BitcoinKey {
             BitcoinKey::XOnlyPublicKey(_) => false,
         }
     }
+    fn is_x_only_key(&self) -> bool { false }
+    fn num_der_paths(&self) -> usize { 0 }
 }
 
 impl<'txin> Interpreter<'txin> {
diff --git a/src/lib.rs b/src/lib.rs
index 01472a2df..0a67f7e85 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -155,16 +155,16 @@ pub use crate::primitives::relative_locktime::{RelLockTime, RelLockTimeError};
 
 /// Trait representing a key which can be converted to a hash type.
 pub trait MiniscriptKey: Clone + Eq + Ord + fmt::Debug + fmt::Display + hash::Hash {
-    /// Returns true if the key is serialized uncompressed, defaults to `false`.
-    fn is_uncompressed(&self) -> bool { false }
+    /// Returns true if the key is serialized uncompressed.
+    fn is_uncompressed(&self) -> bool;
 
-    /// Returns true if the key is an x-only pubkey, defaults to `false`.
-    fn is_x_only_key(&self) -> bool { false }
+    /// Returns true if the key is an x-only pubkey.
+    fn is_x_only_key(&self) -> bool;
 
-    /// Returns the number of different derivation paths in this key, defaults to `0`.
+    /// Returns the number of different derivation paths in this key.
     ///
     /// Only >1 for keys in BIP389 multipath descriptors.
-    fn num_der_paths(&self) -> usize { 0 }
+    fn num_der_paths(&self) -> usize;
 
     /// The type used in the sha256 fragment.
     type Sha256: Clone + Eq + Ord + fmt::Display + fmt::Debug + hash::Hash;
@@ -184,6 +184,10 @@ impl MiniscriptKey for bitcoin::secp256k1::PublicKey {
     type Hash256 = hash256::Hash;
     type Ripemd160 = ripemd160::Hash;
     type Hash160 = hash160::Hash;
+
+    fn is_uncompressed(&self) -> bool { false }
+    fn is_x_only_key(&self) -> bool { false }
+    fn num_der_paths(&self) -> usize { 0 }
 }
 
 impl MiniscriptKey for bitcoin::PublicKey {
@@ -193,6 +197,8 @@ impl MiniscriptKey for bitcoin::PublicKey {
     type Hash160 = hash160::Hash;
 
     fn is_uncompressed(&self) -> bool { !self.compressed }
+    fn is_x_only_key(&self) -> bool { false }
+    fn num_der_paths(&self) -> usize { 0 }
 }
 
 impl MiniscriptKey for bitcoin::secp256k1::XOnlyPublicKey {
@@ -201,7 +207,9 @@ impl MiniscriptKey for bitcoin::secp256k1::XOnlyPublicKey {
     type Ripemd160 = ripemd160::Hash;
     type Hash160 = hash160::Hash;
 
+    fn is_uncompressed(&self) -> bool { false }
     fn is_x_only_key(&self) -> bool { true }
+    fn num_der_paths(&self) -> usize { 0 }
 }
 
 impl MiniscriptKey for String {
@@ -209,6 +217,10 @@ impl MiniscriptKey for String {
     type Hash256 = String;
     type Ripemd160 = String;
     type Hash160 = String;
+
+    fn is_uncompressed(&self) -> bool { false }
+    fn is_x_only_key(&self) -> bool { false }
+    fn num_der_paths(&self) -> usize { 0 }
 }
 
 /// Trait describing key types that can be converted to bitcoin public keys.