diff --git a/src/mdbx.c b/src/mdbx.c
index 89fe3cee..eb1478be 100644
--- a/src/mdbx.c
+++ b/src/mdbx.c
@@ -4188,8 +4188,9 @@ static int mdbx_sync_locked(MDBX_env *env, unsigned flags,
   if ((flags & (MDBX_NOSYNC | MDBX_NOMETASYNC)) == 0) {
     mdbx_assert(env, ((flags ^ env->me_flags) & MDBX_WRITEMAP) == 0);
     if (flags & MDBX_WRITEMAP) {
-      const size_t offset = (uint8_t *)container_of(head, MDBX_page, mp_meta) -
-                            env->me_dxb_mmap.dxb;
+      const size_t offset =
+          ((uint8_t *)container_of(head, MDBX_page, mp_meta)) -
+          env->me_dxb_mmap.dxb;
       const size_t paged_offset = offset & ~(env->me_os_psize - 1);
       const size_t paged_length = mdbx_roundup2(
           env->me_psize + offset - paged_offset, env->me_os_psize);
@@ -4852,7 +4853,7 @@ static int __cold mdbx_setup_dxb(MDBX_env *env, int lck_rc) {
         head->mm_datasync_sign = MDBX_DATASIGN_WEAK;
         head->mm_txnid_b = 0;
         const size_t offset =
-            (uint8_t *)container_of(head, MDBX_page, mp_meta) -
+            ((uint8_t *)container_of(head, MDBX_page, mp_meta)) -
             env->me_dxb_mmap.dxb;
         const size_t paged_offset = offset & ~(env->me_os_psize - 1);
         const size_t paged_length = mdbx_roundup2(
@@ -10750,9 +10751,10 @@ int mdbx_txn_straggler(MDBX_txn *txn, int *percent)
 
   MDBX_env *env = txn->mt_env;
   if (unlikely((txn->mt_flags & MDBX_RDONLY) == 0)) {
-    *percent =
-        (int)((txn->mt_next_pgno * UINT64_C(100) + txn->mt_end_pgno / 2) /
-              txn->mt_end_pgno);
+    if (percent)
+      *percent =
+          (int)((txn->mt_next_pgno * UINT64_C(100) + txn->mt_end_pgno / 2) /
+                txn->mt_end_pgno);
     return -1;
   }
 
diff --git a/src/osal.c b/src/osal.c
index c3b50c92..d9026cfa 100644
--- a/src/osal.c
+++ b/src/osal.c
@@ -17,6 +17,8 @@
 #include "./bits.h"
 
 #if defined(_WIN32) || defined(_WIN64)
+#include <winternl.h>
+
 static int waitstatus2errcode(DWORD result) {
   switch (result) {
   case WAIT_OBJECT_0:
@@ -53,25 +55,6 @@ static int ntstatus2errcode(NTSTATUS status) {
  * ntdll.dll, which is not linked by default in user code. */
 #pragma comment(lib, "ntdll.lib")
 
-#ifndef NT_SUCCESS
-#define NT_SUCCESS(x) ((x) >= 0)
-#define STATUS_SUCCESS ((NTSTATUS)0)
-#endif
-typedef struct _UNICODE_STRING {
-  USHORT Length;
-  USHORT MaximumLength;
-  PWSTR Buffer;
-} UNICODE_STRING, *PUNICODE_STRING;
-
-typedef struct _OBJECT_ATTRIBUTES {
-  ULONG Length;
-  HANDLE RootDirectory;
-  PUNICODE_STRING ObjectName;
-  ULONG Attributes;
-  PVOID SecurityDescriptor;
-  PVOID SecurityQualityOfService;
-} OBJECT_ATTRIBUTES, *POBJECT_ATTRIBUTES;
-
 extern NTSTATUS NTAPI NtCreateSection(
     OUT PHANDLE SectionHandle, IN ACCESS_MASK DesiredAccess,
     IN OPTIONAL POBJECT_ATTRIBUTES ObjectAttributes,
@@ -104,14 +87,6 @@ extern NTSTATUS NTAPI NtFreeVirtualMemory(IN HANDLE ProcessHandle,
                                           IN OUT PULONG RegionSize,
                                           IN ULONG FreeType);
 
-typedef struct _IO_STATUS_BLOCK {
-  union {
-    NTSTATUS Status;
-    PVOID Pointer;
-  };
-  ULONG_PTR Information;
-} IO_STATUS_BLOCK, *PIO_STATUS_BLOCK;
-
 #ifndef FILE_PROVIDER_CURRENT_VERSION
 typedef struct _FILE_PROVIDER_EXTERNAL_INFO_V1 {
   ULONG Version;
diff --git a/tutorial/sample-mdbx.c b/tutorial/sample-mdbx.c
index 39adba02..f5188cf4 100644
--- a/tutorial/sample-mdbx.c
+++ b/tutorial/sample-mdbx.c
@@ -37,7 +37,7 @@ int main(int argc, char *argv[]) {
   rc = mdbx_env_create(&env);
   if (rc != MDBX_SUCCESS) {
     fprintf(stderr, "mdbx_env_create: (%d) %s\n", rc, mdbx_strerror(rc));
-    return 0;
+    goto bailout;
   }
   rc = mdbx_env_open(env, "./example-db",
                      MDBX_NOSUBDIR | MDBX_COALESCE | MDBX_LIFORECLAIM, 0664);