diff --git a/src/osal.h b/src/osal.h
index 239d3f95..b3eda1c0 100644
--- a/src/osal.h
+++ b/src/osal.h
@@ -180,9 +180,6 @@ static inline void osal_free(void *ptr) { HeapFree(GetProcessHeap(), 0, ptr); }
 #define vsnprintf _vsnprintf /* ntdll */
 #endif
 
-MDBX_INTERNAL_FUNC size_t osal_mb2w(wchar_t *dst, size_t dst_n, const char *src,
-                                    size_t src_n);
-
 #else /*----------------------------------------------------------------------*/
 
 typedef pthread_t osal_thread_t;
@@ -702,6 +699,9 @@ MDBX_INTERNAL_FUNC int osal_rpid_check(MDBX_env *env, uint32_t pid);
 
 #if defined(_WIN32) || defined(_WIN64)
 
+MDBX_INTERNAL_FUNC size_t osal_mb2w(wchar_t *dst, size_t dst_n, const char *src,
+                                    size_t src_n);
+
 #define OSAL_MB2WIDE(FROM, TO)                                                 \
   do {                                                                         \
     const char *const from_tmp = (FROM);                                       \