diff --git a/src/move.c b/src/move.c
index 69091fd..aa90b52 100644
--- a/src/move.c
+++ b/src/move.c
@@ -541,6 +541,8 @@
 #endif
     // Approximate the value of w_botline
     wp->w_botline += lnum - wp->w_topline;
+    if (wp->w_botline > wp->w_buffer->b_ml.ml_line_count + 1)
+	wp->w_botline = wp->w_buffer->b_ml.ml_line_count + 1;
     wp->w_topline = lnum;
     wp->w_topline_was_set = TRUE;
 #ifdef FEAT_DIFF
@@ -595,8 +597,17 @@
     void
 validate_botline(void)
 {
-    if (!(curwin->w_valid & VALID_BOTLINE))
-	comp_botline(curwin);
+    validate_botline_win(curwin);
+}
+
+/*
+ * Make sure the value of wp->w_botline is valid.
+ */
+    void
+validate_botline_win(win_T *wp)
+{
+    if (!(wp->w_valid & VALID_BOTLINE))
+	comp_botline(wp);
 }
 
 /*