diff --git a/vertx-mssql-client/src/test/java/io/vertx/tests/mssqlclient/MSSQLQueriesTest.java b/vertx-mssql-client/src/test/java/io/vertx/tests/mssqlclient/MSSQLQueriesTest.java
index 07b645cab..9e0b4869e 100644
--- a/vertx-mssql-client/src/test/java/io/vertx/tests/mssqlclient/MSSQLQueriesTest.java
+++ b/vertx-mssql-client/src/test/java/io/vertx/tests/mssqlclient/MSSQLQueriesTest.java
@@ -40,8 +40,7 @@
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
-import static org.hamcrest.CoreMatchers.instanceOf;
-import static org.hamcrest.CoreMatchers.is;
+import static org.hamcrest.CoreMatchers.*;
 import static org.hamcrest.MatcherAssert.assertThat;
 
 @RunWith(VertxUnitRunner.class)
@@ -206,4 +205,22 @@ public void testQuerySequences(TestContext ctx) {
         }));
     }));
   }
+
+  @Test
+  public void testUnsupportedXmlTypeErrorPropagation(TestContext ctx) {
+    connection
+      .query("CREATE TABLE #TempXmlTest (id INT, xmlData XML)")
+      .execute()
+      .onComplete(ctx.asyncAssertSuccess(create -> {
+        connection
+          .query("SELECT * FROM #TempXmlTest")
+          .execute()
+          .onComplete(ctx.asyncAssertFailure(t -> {
+            ctx.verify(v -> {
+              assertThat(t, instanceOf(UnsupportedOperationException.class));
+              assertThat(t.getMessage(), containsString("XML"));
+            });
+          }));
+      }));
+  }
 }
diff --git a/vertx-pg-client/src/main/java/io/vertx/pgclient/impl/codec/InitPgCommandMessage.java b/vertx-pg-client/src/main/java/io/vertx/pgclient/impl/codec/InitPgCommandMessage.java
index 4f1c11bce..5def14084 100644
--- a/vertx-pg-client/src/main/java/io/vertx/pgclient/impl/codec/InitPgCommandMessage.java
+++ b/vertx-pg-client/src/main/java/io/vertx/pgclient/impl/codec/InitPgCommandMessage.java
@@ -16,19 +16,19 @@
  */
 package io.vertx.pgclient.impl.codec;
 
-import java.nio.charset.Charset;
-import java.nio.charset.StandardCharsets;
-
 import io.netty.buffer.ByteBuf;
 import io.vertx.core.VertxException;
 import io.vertx.pgclient.impl.PgDatabaseMetadata;
 import io.vertx.pgclient.impl.PgSocketConnection;
 import io.vertx.pgclient.impl.auth.scram.ScramAuthentication;
 import io.vertx.pgclient.impl.auth.scram.ScramSession;
-import io.vertx.sqlclient.spi.connection.Connection;
 import io.vertx.sqlclient.codec.CommandResponse;
+import io.vertx.sqlclient.spi.connection.Connection;
 import io.vertx.sqlclient.spi.protocol.InitCommand;
 
+import java.nio.charset.Charset;
+import java.nio.charset.StandardCharsets;
+
 class InitPgCommandMessage extends PgCommandMessage<Connection, InitCommand> {
 
   private PgEncoder encoder;
@@ -65,9 +65,17 @@ void handleAuthenticationSasl(ByteBuf in) {
       throw new VertxException("Scram authentication not supported, missing com.ongres.scram:scram-client on the class/module path");
     }
     scramSession = scramAuth.session(cmd.username(), cmd.password().toCharArray());
-    encoder.writeScramClientInitialMessage(
+    try {
+      encoder.writeScramClientInitialMessage(
         scramSession.createInitialSaslMessage(in, encoder.channelHandlerContext()));
-    encoder.flush();
+      encoder.flush();
+    } catch (RuntimeException e) {
+      decoder.fireCommandResponse(CommandResponse.failure(e));
+      // If the frontend does not support the authentication method requested by the server,
+      // then it should immediately close the connection.
+      // See https://www.postgresql.org/docs/current/protocol-flow.html
+      encoder.close();
+    }
   }
 
   @Override
diff --git a/vertx-pg-client/src/test/java/io/vertx/tests/pgclient/PgConnectionTest.java b/vertx-pg-client/src/test/java/io/vertx/tests/pgclient/PgConnectionTest.java
index b7b0043bd..f57a63bd1 100644
--- a/vertx-pg-client/src/test/java/io/vertx/tests/pgclient/PgConnectionTest.java
+++ b/vertx-pg-client/src/test/java/io/vertx/tests/pgclient/PgConnectionTest.java
@@ -20,7 +20,7 @@
 import io.vertx.ext.unit.Async;
 import io.vertx.ext.unit.TestContext;
 import io.vertx.pgclient.PgConnection;
-import io.vertx.sqlclient.ClosedConnectionException;
+import io.vertx.pgclient.PgException;
 import io.vertx.sqlclient.Row;
 import io.vertx.sqlclient.RowSet;
 import io.vertx.sqlclient.Tuple;
@@ -148,7 +148,12 @@ public void testInflightCommandsFailWhenConnectionClosed(TestContext ctx) {
             .query("SELECT pg_sleep(20)")
             .execute()
             .onComplete(ctx.asyncAssertFailure(t -> {
-              ctx.assertTrue(t instanceof ClosedConnectionException);
+              if (t instanceof PgException) {
+                PgException pge = (PgException) t;
+                ctx.assertEquals("57P01", pge.getSqlState()); // ADMIN SHUTDOWN
+              } else {
+                ctx.fail(t);
+              }
             }));
           connector.accept(ctx.asyncAssertSuccess(conn2 -> {
             conn2
diff --git a/vertx-sql-client-codec/src/main/java/io/vertx/sqlclient/codec/SocketConnectionBase.java b/vertx-sql-client-codec/src/main/java/io/vertx/sqlclient/codec/SocketConnectionBase.java
index 85b912b40..e3ee9414a 100644
--- a/vertx-sql-client-codec/src/main/java/io/vertx/sqlclient/codec/SocketConnectionBase.java
+++ b/vertx-sql-client-codec/src/main/java/io/vertx/sqlclient/codec/SocketConnectionBase.java
@@ -21,28 +21,25 @@
 import io.netty.channel.ChannelFutureListener;
 import io.netty.channel.ChannelHandlerContext;
 import io.netty.handler.codec.DecoderException;
-import io.vertx.core.*;
+import io.vertx.core.Completable;
+import io.vertx.core.Vertx;
+import io.vertx.core.VertxException;
+import io.vertx.core.internal.ContextInternal;
 import io.vertx.core.internal.logging.Logger;
 import io.vertx.core.internal.logging.LoggerFactory;
+import io.vertx.core.internal.net.NetSocketInternal;
 import io.vertx.core.net.SocketAddress;
 import io.vertx.core.spi.metrics.ClientMetrics;
 import io.vertx.core.tracing.TracingPolicy;
-import io.vertx.core.internal.ContextInternal;
-import io.vertx.core.internal.net.NetSocketInternal;
 import io.vertx.sqlclient.ClosedConnectionException;
 import io.vertx.sqlclient.Row;
 import io.vertx.sqlclient.SqlConnectOptions;
 import io.vertx.sqlclient.codec.impl.PreparedStatementCache;
-import io.vertx.sqlclient.spi.connection.Connection;
 import io.vertx.sqlclient.internal.PreparedStatement;
 import io.vertx.sqlclient.spi.DatabaseMetadata;
+import io.vertx.sqlclient.spi.connection.Connection;
 import io.vertx.sqlclient.spi.connection.ConnectionContext;
-import io.vertx.sqlclient.spi.protocol.CloseConnectionCommand;
-import io.vertx.sqlclient.spi.protocol.CloseStatementCommand;
-import io.vertx.sqlclient.spi.protocol.CommandBase;
-import io.vertx.sqlclient.spi.protocol.CompositeCommand;
-import io.vertx.sqlclient.spi.protocol.ExtendedQueryCommand;
-import io.vertx.sqlclient.spi.protocol.PrepareStatementCommand;
+import io.vertx.sqlclient.spi.protocol.*;
 
 import java.util.ArrayDeque;
 import java.util.List;
@@ -437,11 +434,12 @@ private void handleClose(Throwable t) {
       if (t != null) {
         reportException(t);
       }
+      Throwable inflightCause = t != null ? t : ClosedConnectionException.INSTANCE;
       CommandMessage<?, ?> msg;
       while ((msg = inflights.poll()) != null) {
-        fail(msg, ClosedConnectionException.INSTANCE);
+        fail(msg, inflightCause);
       }
-      Throwable cause = t == null ? VertxException.noStackTrace(PENDING_CMD_CONNECTION_CORRUPT_MSG) : new VertxException(PENDING_CMD_CONNECTION_CORRUPT_MSG, t);
+      Throwable cause = t == null ? VertxException.noStackTrace(PENDING_CMD_CONNECTION_CORRUPT_MSG) : VertxException.noStackTrace(PENDING_CMD_CONNECTION_CORRUPT_MSG, t);
       CommandBase<?> cmd;
       while ((cmd = pending.poll()) != null) {
         CommandBase c = cmd;