diff --git a/NBitcoin.Tests/MiniscriptTests.cs b/NBitcoin.Tests/MiniscriptTests.cs
index d760f1739..d44881443 100644
--- a/NBitcoin.Tests/MiniscriptTests.cs
+++ b/NBitcoin.Tests/MiniscriptTests.cs
@@ -71,6 +71,21 @@ public void CanRoundtripMiniscript(string miniscript)
 			Assert.Equal(miniscript, actual);
 		}
 
+		[Theory]
+		// https://github.com/MetacoSA/NBitcoin/issues/1283
+		[InlineData("older(000000002088829000)", false)]
+		[InlineData("older(01)", false)]
+		[InlineData("after(01)", false)]
+		[InlineData("multi(01,A,B)", false)]
+		[InlineData("older(0)", true)]
+		[InlineData("older(1000)", true)]
+		[InlineData("after(1000)", true)]
+		public void RejectsNonCanonicalNumbers(string miniscript, bool expected)
+		{
+			var settings = new MiniscriptParsingSettings(Network.RegTest, KeyType.Classic) { AllowedParameters = ParameterTypeFlags.All };
+			Assert.Equal(expected, Miniscript.TryParse(miniscript, settings, out _));
+		}
+
 		[Theory]
 		[InlineData(ParameterTypeFlags.All, "pkh(A)", true)]
 		[InlineData(ParameterTypeFlags.All, "pkh(@0/**)", true)]
diff --git a/NBitcoin/WalletPolicies/Miniscript.cs b/NBitcoin/WalletPolicies/Miniscript.cs
index 358534495..25462a4e1 100644
--- a/NBitcoin/WalletPolicies/Miniscript.cs
+++ b/NBitcoin/WalletPolicies/Miniscript.cs
@@ -222,6 +222,11 @@ private static bool TryParseParameterCount(ParsingContext ctx, [MaybeNullWhen(tr
 			error = null;
 			node = null;
 			var match = Regex.Match(ctx.Remaining, @"^[0-9]+");
+			if (match.Value.Length > 1 && match.Value[0] == '0')
+			{
+				error = new MiniscriptError.CountExpected(ctx.Offset);
+				return false;
+			}
 			if (uint.TryParse(match.Value, NumberStyles.Integer, CultureInfo.InvariantCulture, out var v) && v < Int32.MaxValue)
 			{
 				ctx.Advance(match.Length);
@@ -257,6 +262,11 @@ private static bool TryParseLocktime(ParsingContext ctx, [MaybeNullWhen(true)] o
 			node = null;
 			error = null;
 			var match = Regex.Match(ctx.Remaining, @"^[0-9]+");
+			if (match.Value.Length > 1 && match.Value[0] == '0')
+			{
+				error = new MiniscriptError.LocktimeExpected(ctx.Offset);
+				return false;
+			}
 			if (uint.TryParse(match.Value, NumberStyles.Integer, CultureInfo.InvariantCulture, out var v))
 			{
 				ctx.Advance(match.Length);