diff --git a/.github/workflows/master.yml b/.github/workflows/master.yml
index d5ab189b0..e5754b26a 100644
--- a/.github/workflows/master.yml
+++ b/.github/workflows/master.yml
@@ -23,6 +23,10 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
+      - name: Install libssl
+        run: |
+          wget http://archive.ubuntu.com/ubuntu/pool/main/o/openssl1.0/libssl1.0.0_1.0.2n-1ubuntu5_amd64.deb
+          sudo dpkg -i libssl1.0.0_1.0.2n-1ubuntu5_amd64.deb
       - uses: actions/setup-dotnet@v1
         with:
           dotnet-version: '6.0.x'
diff --git a/NBitcoin/NBitcoin.csproj b/NBitcoin/NBitcoin.csproj
index 716cb6110..8c2ec5e65 100644
--- a/NBitcoin/NBitcoin.csproj
+++ b/NBitcoin/NBitcoin.csproj
@@ -12,7 +12,7 @@
 		<RepositoryType>git</RepositoryType>
 	</PropertyGroup>
 	<PropertyGroup>
-		<Version Condition=" '$(Version)' == '' ">7.0.42</Version>
+		<Version Condition=" '$(Version)' == '' ">7.0.42.1</Version>
 		<LangVersion>9.0</LangVersion>
 	</PropertyGroup>
 	<PropertyGroup Condition=" '$(Configuration)' == 'Release' ">
diff --git a/NBitcoin/RPC/RPCClient.cs b/NBitcoin/RPC/RPCClient.cs
index 8e576363e..9db668e60 100644
--- a/NBitcoin/RPC/RPCClient.cs
+++ b/NBitcoin/RPC/RPCClient.cs
@@ -2029,7 +2029,7 @@ public async Task<BumpResponse> BumpFeeAsync(uint256 txid, CancellationToken can
 		/// <param name="estimateMode">Whether to return a more conservative estimate which also satisfies a longer history. A conservative estimate potentially returns a higher feerate and is more likely to be sufficient for the desired target, but is not as responsive to short term drops in the prevailing fee market.</param>
 		/// <returns>The estimated fee rate, block number where estimate was found</returns>
 		/// <exception cref="NoEstimationException">The Fee rate couldn't be estimated because of insufficient data from Bitcoin Core</exception>
-		public EstimateSmartFeeResponse EstimateSmartFee(int confirmationTarget, EstimateSmartFeeMode estimateMode = EstimateSmartFeeMode.Conservative)
+		public EstimateSmartFeeResponse EstimateSmartFee(int confirmationTarget, EstimateSmartFeeMode? estimateMode = null)
 		{
 			return EstimateSmartFeeAsync(confirmationTarget, estimateMode).GetAwaiter().GetResult();
 		}
@@ -2041,7 +2041,7 @@ public EstimateSmartFeeResponse EstimateSmartFee(int confirmationTarget, Estimat
 		/// <param name="confirmationTarget">Confirmation target in blocks (1 - 1008)</param>
 		/// <param name="estimateMode">Whether to return a more conservative estimate which also satisfies a longer history. A conservative estimate potentially returns a higher feerate and is more likely to be sufficient for the desired target, but is not as responsive to short term drops in the prevailing fee market.</param>
 		/// <returns>The estimated fee rate, block number where estimate was found or null</returns>
-		public async Task<EstimateSmartFeeResponse> TryEstimateSmartFeeAsync(int confirmationTarget, EstimateSmartFeeMode estimateMode = EstimateSmartFeeMode.Conservative, CancellationToken cancellationToken = default)
+		public async Task<EstimateSmartFeeResponse> TryEstimateSmartFeeAsync(int confirmationTarget, EstimateSmartFeeMode? estimateMode = null, CancellationToken cancellationToken = default)
 		{
 			return await EstimateSmartFeeImplAsync(confirmationTarget, estimateMode, cancellationToken).ConfigureAwait(false);
 		}
@@ -2053,7 +2053,7 @@ public async Task<EstimateSmartFeeResponse> TryEstimateSmartFeeAsync(int confirm
 		/// <param name="confirmationTarget">Confirmation target in blocks (1 - 1008)</param>
 		/// <param name="estimateMode">Whether to return a more conservative estimate which also satisfies a longer history. A conservative estimate potentially returns a higher feerate and is more likely to be sufficient for the desired target, but is not as responsive to short term drops in the prevailing fee market.</param>
 		/// <returns>The estimated fee rate, block number where estimate was found or null</returns>
-		public EstimateSmartFeeResponse TryEstimateSmartFee(int confirmationTarget, EstimateSmartFeeMode estimateMode = EstimateSmartFeeMode.Conservative)
+		public EstimateSmartFeeResponse TryEstimateSmartFee(int confirmationTarget, EstimateSmartFeeMode? estimateMode = null)
 		{
 			return TryEstimateSmartFeeAsync(confirmationTarget, estimateMode).GetAwaiter().GetResult();
 		}
@@ -2066,7 +2066,7 @@ public EstimateSmartFeeResponse TryEstimateSmartFee(int confirmationTarget, Esti
 		/// <param name="estimateMode">Whether to return a more conservative estimate which also satisfies a longer history. A conservative estimate potentially returns a higher feerate and is more likely to be sufficient for the desired target, but is not as responsive to short term drops in the prevailing fee market.</param>
 		/// <returns>The estimated fee rate, block number where estimate was found</returns>
 		/// <exception cref="NoEstimationException">when fee couldn't be estimated</exception>
-		public async Task<EstimateSmartFeeResponse> EstimateSmartFeeAsync(int confirmationTarget, EstimateSmartFeeMode estimateMode = EstimateSmartFeeMode.Conservative, CancellationToken cancellationToken = default)
+		public async Task<EstimateSmartFeeResponse> EstimateSmartFeeAsync(int confirmationTarget, EstimateSmartFeeMode? estimateMode = null, CancellationToken cancellationToken = default)
 		{
 			var feeRate = await EstimateSmartFeeImplAsync(confirmationTarget, estimateMode, cancellationToken);
 			if (feeRate == null)
@@ -2077,12 +2077,12 @@ public async Task<EstimateSmartFeeResponse> EstimateSmartFeeAsync(int confirmati
 		/// <summary>
 		/// (>= Bitcoin Core v0.14)
 		/// </summary>
-		private async Task<EstimateSmartFeeResponse> EstimateSmartFeeImplAsync(int confirmationTarget, EstimateSmartFeeMode estimateMode = EstimateSmartFeeMode.Conservative, CancellationToken cancellationToken = default)
+		private async Task<EstimateSmartFeeResponse> EstimateSmartFeeImplAsync(int confirmationTarget, EstimateSmartFeeMode? estimateMode = null, CancellationToken cancellationToken = default)
 		{
 			if (Capabilities == null || Capabilities.SupportEstimateSmartFee)
 			{
 				var parameters = new List<object>() { confirmationTarget };
-				if (estimateMode != EstimateSmartFeeMode.Conservative)
+				if (estimateMode != null)
 				{
 					parameters.Add(estimateMode.ToString().ToUpperInvariant());
 				}