diff --git a/modules/bitcoind.nix b/modules/bitcoind.nix
index eab5b40..cc073e1 100644
--- a/modules/bitcoind.nix
+++ b/modules/bitcoind.nix
@@ -19,7 +19,7 @@ let
     listen=${if cfg.listen then "1" else "0"}
 
     # RPC server options
-    ${optionalString (cfg.rpc.port != null) "rpcport=${toString cfg.rpc.port}"}
+    rpcport=${toString cfg.rpc.port}
     ${concatMapStringsSep  "\n"
       (rpcUser: "rpcauth=${rpcUser.name}:${rpcUser.passwordHMAC}")
       (attrValues cfg.rpc.users)
@@ -108,9 +108,9 @@ in {
 
       rpc = {
         port = mkOption {
-          type = types.nullOr types.ints.u16;
-          default = null;
-          description = "Override the default port on which to listen for JSON-RPC connections.";
+          type = types.ints.u16;
+          default = 8332;
+          description = "Port on which to listen for JSON-RPC connections.";
         };
         users = mkOption {
           default = {};
@@ -241,6 +241,12 @@ in {
         echo "rpcpassword=$(cat /secrets/bitcoin-rpcpassword)" >> '${cfg.dataDir}/bitcoin.conf'
         chmod -R g+rX '${cfg.dataDir}/blocks'
       '';
+      # Wait until RPC port is open. This usually takes just a few ms.
+      postStart = ''
+        while ! { exec 3>/dev/tcp/127.0.0.1/${toString cfg.rpc.port}; } &>/dev/null; do
+          sleep 0.05
+        done
+      '';
       serviceConfig = {
         Type = "simple";
         User = "${cfg.user}";