diff --git a/src/lib.rs b/src/lib.rs
index 20b0e4331..fde7ac66b 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -423,10 +423,6 @@ pub enum Error {
     AddrError(bitcoin::address::ParseError),
     /// rust-bitcoin p2sh address error
     AddrP2shError(bitcoin::address::P2shError),
-    /// A `CHECKMULTISIG` opcode was preceded by a number > 20
-    CmsTooManyKeys(u32),
-    /// A tapscript multi_a cannot support more than Weight::MAX_BLOCK/32 keys
-    MultiATooManyKeys(u64),
     /// While parsing backward, hit beginning of script
     UnexpectedStart,
     /// Got something we were not expecting
@@ -504,7 +500,6 @@ impl fmt::Display for Error {
             Error::Script(ref e) => fmt::Display::fmt(e, f),
             Error::AddrError(ref e) => fmt::Display::fmt(e, f),
             Error::AddrP2shError(ref e) => fmt::Display::fmt(e, f),
-            Error::CmsTooManyKeys(n) => write!(f, "checkmultisig with {} keys", n),
             Error::UnexpectedStart => f.write_str("unexpected start of script"),
             Error::Unexpected(ref s) => write!(f, "unexpected «{}»", s),
             Error::MultiColon(ref s) => write!(f, "«{}» has multiple instances of «:»", s),
@@ -539,7 +534,6 @@ impl fmt::Display for Error {
             Error::PubKeyCtxError(ref pk, ref ctx) => {
                 write!(f, "Pubkey error: {} under {} scriptcontext", pk, ctx)
             }
-            Error::MultiATooManyKeys(k) => write!(f, "MultiA too many keys {}", k),
             Error::TrNoScriptCode => write!(f, "No script code for Tr descriptors"),
             Error::MultipathDescLenMismatch => write!(f, "At least two BIP389 key expressions in the descriptor contain tuples of derivation indexes of different lengths"),
             Error::AbsoluteLockTime(ref e) => e.fmt(f),
@@ -560,8 +554,6 @@ impl std::error::Error for Error {
             InvalidOpcode(_)
             | NonMinimalVerify(_)
             | InvalidPush(_)
-            | CmsTooManyKeys(_)
-            | MultiATooManyKeys(_)
             | UnexpectedStart
             | Unexpected(_)
             | MultiColon(_)
diff --git a/src/miniscript/decode.rs b/src/miniscript/decode.rs
index 0090b7516..17e81112a 100644
--- a/src/miniscript/decode.rs
+++ b/src/miniscript/decode.rs
@@ -538,10 +538,10 @@ pub fn parse<Ctx: ScriptContext>(
                     },
                     // CHECKMULTISIG based multisig
                     Tk::CheckMultiSig, Tk::Num(n) => {
-                        // Check size before allocating keys
-                        if n as usize > MAX_PUBKEYS_PER_MULTISIG {
-                            return Err(Error::CmsTooManyKeys(n));
-                        }
+                        // Check size before allocating keys. Note that constructing a
+                        // vector of ()s, no matter the size, takes no allocations.
+                        Threshold::<(), MAX_PUBKEYS_PER_MULTISIG>::new(1, vec![(); n as usize]).map_err(Error::Threshold)?;
+
                         let mut keys = Vec::with_capacity(n as usize);
                         for _ in 0..n {
                             match_token!(
@@ -562,10 +562,10 @@ pub fn parse<Ctx: ScriptContext>(
                     },
                     // MultiA
                     Tk::NumEqual, Tk::Num(k) => {
-                        // Check size before allocating keys
-                        if k as usize > MAX_PUBKEYS_IN_CHECKSIGADD {
-                            return Err(Error::MultiATooManyKeys(MAX_PUBKEYS_IN_CHECKSIGADD as u64))
-                        }
+                        // Check size before allocating keys. Note that constructing a
+                        // vector of ()s, no matter the size, takes no allocations.
+                        Threshold::<(), MAX_PUBKEYS_IN_CHECKSIGADD>::new(k as usize, vec![(); k as usize]).map_err(Error::Threshold)?;
+
                         let mut keys = Vec::with_capacity(k as usize); // atleast k capacity
                         while tokens.peek() == Some(&Tk::CheckSigAdd) {
                             match_token!(