diff --git a/src/lTerm.ml b/src/lTerm.ml
index 32770d6..9df007a 100644
--- a/src/lTerm.ml
+++ b/src/lTerm.ml
@@ -210,16 +210,24 @@ let create
     term.input_stream <- Lwt_stream.from (fun () -> Lwt_io.read_char_opt term.ic);
     (* Setup initial size and size updater. *)
     if term.outgoing_is_a_tty then begin
-      let check_size () =
-        let size = get_size_from_fd term.outgoing_fd in
-        if size <> term.size then begin
-          term.size <- size;
-          Lwt_condition.signal term.notify (LTerm_event.Resize size)
-        end
-      in
-      term.size <- get_size_from_fd term.outgoing_fd;
-      term.last_reported_size <- term.size;
-      term.event <- E.map check_size resize_event
+      try
+        let check_size () =
+          try
+            let size = get_size_from_fd term.outgoing_fd in
+            if size <> term.size then begin
+              term.size <- size;
+              Lwt_condition.signal term.notify (LTerm_event.Resize size)
+            end
+          with Unix.Unix_error _ -> ()
+        in
+        term.size <- get_size_from_fd term.outgoing_fd;
+        term.last_reported_size <- term.size;
+        term.event <- E.map check_size resize_event
+      with Unix.Unix_error _ ->
+        (* If we can't get the terminal size (e.g. on Windows when the
+           handle passes isatty but is not a real console), fall back to
+           treating it as a non-tty. *)
+        term.outgoing_is_a_tty <- false
     end;
     return term)
     Lwt.fail
diff --git a/src/lTerm_term_stubs.c b/src/lTerm_term_stubs.c
index 002c36d..20901b3 100644
--- a/src/lTerm_term_stubs.c
+++ b/src/lTerm_term_stubs.c
@@ -23,10 +23,22 @@
 
 CAMLprim value lt_term_get_size_from_fd(value fd)
 {
+  HANDLE h = Handle_val(fd);
   CONSOLE_SCREEN_BUFFER_INFO info;
+  DWORD mode;
   value result;
 
-  if (!GetConsoleScreenBufferInfo(Handle_val(fd), &info)) {
+  /* Validate that the handle is a usable console handle before calling
+     GetConsoleScreenBufferInfo. On some Windows environments (e.g. GitHub
+     Actions runners using ConPTY), _isatty() may return true for handles
+     that are not real console screen buffers, causing
+     GetConsoleScreenBufferInfo to crash with an access violation. */
+  if (h == INVALID_HANDLE_VALUE || h == NULL || !GetConsoleMode(h, &mode)) {
+    win32_maperr(ERROR_INVALID_HANDLE);
+    uerror("GetConsoleScreenBufferInfo", Nothing);
+  }
+
+  if (!GetConsoleScreenBufferInfo(h, &info)) {
     win32_maperr(GetLastError());
     uerror("GetConsoleScreenBufferInfo", Nothing);
   }
@@ -39,21 +51,28 @@ CAMLprim value lt_term_get_size_from_fd(value fd)
 
 CAMLprim value lt_term_set_size_from_fd(value fd, value val_size)
 {
+  HANDLE h = Handle_val(fd);
   CONSOLE_SCREEN_BUFFER_INFO info;
   SMALL_RECT rect;
+  DWORD mode;
+
+  /* Validate that the handle is a usable console handle. */
+  if (h == INVALID_HANDLE_VALUE || h == NULL || !GetConsoleMode(h, &mode)) {
+    win32_maperr(ERROR_INVALID_HANDLE);
+    uerror("SetConsoleWindowInfo", Nothing);
+  }
 
-  if (!GetConsoleScreenBufferInfo(Handle_val(fd), &info)) {
+  if (!GetConsoleScreenBufferInfo(h, &info)) {
     win32_maperr(GetLastError());
     uerror("GetConsoleScreenBufferInfo", Nothing);
   }
 
-  rect;
   rect.Top = info.srWindow.Top;
   rect.Left = info.srWindow.Left;
   rect.Bottom = rect.Top + Int_val(Field(val_size, 0)) - 1;
   rect.Right = rect.Left + Int_val(Field(val_size, 1)) - 1;
 
-  if (!SetConsoleWindowInfo(Handle_val(fd), TRUE, &rect)) {
+  if (!SetConsoleWindowInfo(h, TRUE, &rect)) {
     win32_maperr(GetLastError());
     uerror("SetConsoleWindowInfo", Nothing);
   }