diff --git a/Cargo.toml b/Cargo.toml
index 081e6491c..05888a538 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -13,7 +13,7 @@ license = "MIT/Apache-2.0"
 name = "tiberius"
 readme = "README.md"
 repository = "https://github.com/prisma/tiberius"
-version = "0.12.2"
+version = "0.12.3"
 
 [workspace]
 members = ["runtimes-macro"]
@@ -52,7 +52,6 @@ connection-string = "0.2"
 num-traits = "0.2"
 uuid = "1.0"
 
-[target.'cfg(windows)'.dependencies]
 winauth = { version = "0.0.4", optional = true }
 
 [target.'cfg(unix)'.dependencies]
@@ -135,6 +134,13 @@ version = "0.2.1"
 optional = true
 features = ["io-async-std", "vendored"]
 
+# Used by the vendored-openssl backend to load trusted roots from the
+# Windows certificate store: the vendored OpenSSL only probes Unix
+# filesystem paths, so without this it trusts nothing on Windows.
+[target.'cfg(windows)'.dependencies.schannel]
+version = "0.1"
+optional = true
+
 [dev-dependencies.uuid]
 version = "1.0"
 features = ["v4"]
@@ -201,4 +207,4 @@ integrated-auth-gssapi = ["libgssapi"]
 bigdecimal = ["bigdecimal_"]
 rustls = ["tokio-rustls", "tokio-util", "rustls-pemfile", "rustls-native-certs"]
 native-tls = ["async-native-tls"]
-vendored-openssl = ["opentls"]
+vendored-openssl = ["opentls", "schannel"]
diff --git a/src/client/auth.rs b/src/client/auth.rs
index 208d8d060..2003d99ba 100644
--- a/src/client/auth.rs
+++ b/src/client/auth.rs
@@ -26,16 +26,16 @@ impl Debug for SqlServerAuth {
 }
 
 #[derive(Clone, PartialEq, Eq)]
-#[cfg(any(all(windows, feature = "winauth"), doc))]
-#[cfg_attr(feature = "docs", doc(all(windows, feature = "winauth")))]
+#[cfg(any(feature = "winauth", doc))]
+#[cfg_attr(feature = "docs", doc(feature = "winauth"))]
 pub struct WindowsAuth {
     pub(crate) user: String,
     pub(crate) password: String,
     pub(crate) domain: Option<String>,
 }
 
-#[cfg(any(all(windows, feature = "winauth"), doc))]
-#[cfg_attr(feature = "docs", doc(all(windows, feature = "winauth")))]
+#[cfg(any(feature = "winauth", doc))]
+#[cfg_attr(feature = "docs", doc(feature = "winauth"))]
 impl Debug for WindowsAuth {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         f.debug_struct("WindowsAuth")
@@ -52,8 +52,8 @@ pub enum AuthMethod {
     /// Authenticate directly with SQL Server.
     SqlServer(SqlServerAuth),
     /// Authenticate with Windows credentials.
-    #[cfg(any(all(windows, feature = "winauth"), doc))]
-    #[cfg_attr(feature = "docs", doc(cfg(all(windows, feature = "winauth"))))]
+    #[cfg(any(feature = "winauth", doc))]
+    #[cfg_attr(feature = "docs", doc(cfg(feature = "winauth")))]
     Windows(WindowsAuth),
     /// Authenticate as the currently logged in user. On Windows uses SSPI and
     /// Kerberos on Unix platforms.
@@ -84,8 +84,8 @@ impl AuthMethod {
     }
 
     /// Construct a new Windows authentication configuration.
-    #[cfg(any(all(windows, feature = "winauth"), doc))]
-    #[cfg_attr(feature = "docs", doc(cfg(all(windows, feature = "winauth"))))]
+    #[cfg(any(feature = "winauth", doc))]
+    #[cfg_attr(feature = "docs", doc(cfg(feature = "winauth")))]
     pub fn windows(user: impl AsRef<str>, password: impl ToString) -> Self {
         let (domain, user) = match user.as_ref().find('\\') {
             Some(idx) => (Some(&user.as_ref()[..idx]), &user.as_ref()[idx + 1..]),
diff --git a/src/client/connection.rs b/src/client/connection.rs
index c6ce1d66e..6c641c41a 100644
--- a/src/client/connection.rs
+++ b/src/client/connection.rs
@@ -18,7 +18,7 @@ use crate::{
 };
 use asynchronous_codec::Framed;
 use bytes::BytesMut;
-#[cfg(any(windows, feature = "integrated-auth-gssapi"))]
+#[cfg(any(windows, feature = "integrated-auth-gssapi", feature = "winauth"))]
 use codec::TokenSspi;
 use futures_util::io::{AsyncRead, AsyncWrite};
 use futures_util::ready;
@@ -38,7 +38,9 @@ use std::{cmp, fmt::Debug, io, pin::Pin, task};
 use task::Poll;
 use tracing::{event, Level};
 #[cfg(all(windows, feature = "winauth"))]
-use winauth::{windows::NtlmSspiBuilder, NextBytes};
+use winauth::windows::NtlmSspiBuilder;
+#[cfg(feature = "winauth")]
+use winauth::NextBytes;
 
 /// A `Connection` is an abstraction between the [`Client`] and the server. It
 /// can be used as a `Stream` to fetch [`Packet`]s from and to `send` packets
@@ -120,7 +122,7 @@ impl<S: AsyncRead + AsyncWrite + Unpin + Send> Connection<S> {
         TokenStream::new(self).flush_done().await
     }
 
-    #[cfg(any(windows, feature = "integrated-auth-gssapi"))]
+    #[cfg(any(windows, feature = "integrated-auth-gssapi", feature = "winauth"))]
     /// Flush the incoming token stream until receiving `SSPI` token.
     async fn flush_sspi(&mut self) -> crate::Result<TokenSspi> {
         TokenStream::new(self).flush_sspi().await
@@ -381,7 +383,7 @@ impl<S: AsyncRead + AsyncWrite + Unpin + Send> Connection<S> {
 
                 self.send(header, next_token).await?;
             }
-            #[cfg(all(windows, feature = "winauth"))]
+            #[cfg(feature = "winauth")]
             AuthMethod::Windows(auth) => {
                 let spn = self.context.spn().to_string();
                 let builder = winauth::NtlmV2ClientBuilder::new().target_spn(spn);
diff --git a/src/client/tls_stream/opentls_tls_stream.rs b/src/client/tls_stream/opentls_tls_stream.rs
index 1f028669e..76c8c9df0 100644
--- a/src/client/tls_stream/opentls_tls_stream.rs
+++ b/src/client/tls_stream/opentls_tls_stream.rs
@@ -53,6 +53,47 @@ pub(crate) async fn create_tls_stream<S: AsyncRead + AsyncWrite + Unpin + Send>(
         }
         TrustConfig::Default => {
             event!(Level::INFO, "Using default trust configuration.");
+
+            // The vendored OpenSSL discovers root certificates by probing
+            // Unix filesystem paths (openssl-probe), which finds nothing on
+            // Windows — its trust anchors live in registry-backed
+            // certificate stores. Load the ROOT store into the connector so
+            // certificate validation can succeed; the current-user view is
+            // a composite that includes the local-machine store, so certs
+            // installed via certlm.msc (machine) or GP-pushed (e.g. Zscaler)
+            // are picked up automatically. Individual certificates OpenSSL
+            // cannot parse are skipped, matching what rustls-native-certs does.
+            //
+            // NOTE: open_current_user("ROOT") is correct for user-session
+            // processes (e.g. the KeeperDB desktop app). A Windows service
+            // would need open_local_machine("ROOT") instead, since services
+            // run in session 0 and the current-user store may be empty there.
+            #[cfg(windows)]
+            match schannel::cert_store::CertStore::open_current_user("ROOT") {
+                Ok(store) => {
+                    for windows_cert in store.certs() {
+                        match Certificate::from_der(windows_cert.to_der()) {
+                            Ok(root_cert) => {
+                                builder = builder.add_root_certificate(root_cert);
+                            }
+                            Err(e) => {
+                                event!(
+                                    Level::WARN,
+                                    "Skipping an unparseable certificate from the Windows ROOT store: {}",
+                                    e
+                                );
+                            }
+                        }
+                    }
+                }
+                Err(e) => {
+                    event!(
+                        Level::WARN,
+                        "Could not open the Windows ROOT certificate store; certificate validation will have no trusted roots: {}",
+                        e
+                    );
+                }
+            }
         }
     }
 
diff --git a/src/tds/codec/login.rs b/src/tds/codec/login.rs
index 265db381e..0ecc3d2fd 100644
--- a/src/tds/codec/login.rs
+++ b/src/tds/codec/login.rs
@@ -187,7 +187,7 @@ impl<'a> LoginMessage<'a> {
         }
     }
 
-    #[cfg(any(all(unix, feature = "integrated-auth-gssapi"), windows))]
+    #[cfg(any(all(unix, feature = "integrated-auth-gssapi"), windows, feature = "winauth"))]
     pub fn integrated_security(&mut self, bytes: Option<Vec<u8>>) {
         if bytes.is_some() {
             self.option_flags_2.insert(OptionFlag2::IntegratedSecurity);
diff --git a/src/tds/codec/token/token_sspi.rs b/src/tds/codec/token/token_sspi.rs
index 954d6dd8b..ccb078bf2 100644
--- a/src/tds/codec/token/token_sspi.rs
+++ b/src/tds/codec/token/token_sspi.rs
@@ -12,7 +12,7 @@ impl AsRef<[u8]> for TokenSspi {
 }
 
 impl TokenSspi {
-    #[cfg(any(windows, all(unix, feature = "integrated-auth-gssapi")))]
+    #[cfg(any(windows, feature = "winauth", all(unix, feature = "integrated-auth-gssapi")))]
     pub fn new(bytes: Vec<u8>) -> Self {
         Self(bytes)
     }
diff --git a/src/tds/context.rs b/src/tds/context.rs
index 732bac15c..55797e649 100644
--- a/src/tds/context.rs
+++ b/src/tds/context.rs
@@ -62,7 +62,7 @@ impl Context {
         self.spn = Some(format!("MSSQLSvc/{}:{}", host.as_ref(), port));
     }
 
-    #[cfg(any(windows, all(unix, feature = "integrated-auth-gssapi")))]
+    #[cfg(any(windows, feature = "winauth", all(unix, feature = "integrated-auth-gssapi")))]
     pub fn spn(&self) -> &str {
         self.spn.as_deref().unwrap_or("")
     }
diff --git a/src/tds/stream/token.rs b/src/tds/stream/token.rs
index 35ce0658b..87c343174 100644
--- a/src/tds/stream/token.rs
+++ b/src/tds/stream/token.rs
@@ -75,7 +75,7 @@ where
         }
     }
 
-    #[cfg(any(windows, feature = "integrated-auth-gssapi"))]
+    #[cfg(any(windows, feature = "integrated-auth-gssapi", feature = "winauth"))]
     pub(crate) async fn flush_sspi(self) -> crate::Result<TokenSspi> {
         let mut stream = self.try_unfold();
         let mut last_error = None;