diff --git a/src/mark.c b/src/mark.c
index 5e2ac55..72a9a92 100644
--- a/src/mark.c
+++ b/src/mark.c
@@ -1525,6 +1525,9 @@
 		if (idx < 0 && curwin->w_jumplistlen < JUMPLISTSIZE)
 		    /* insert as the oldest entry */
 		    idx = 0;
+		else if (idx == 0 && curwin->w_jumplistlen == JUMPLISTSIZE)
+		    /* no space to insert as the oldest entry */
+		    idx = -1;
 	    }
 	    else if (curwin->w_jumplistlen < JUMPLISTSIZE)
 		/* insert as oldest entry */
@@ -1537,6 +1540,7 @@
 		if (curwin->w_jumplistlen == JUMPLISTSIZE)
 		{
 		    /* Drop the oldest entry. */
+		    --idx;
 		    vim_free(curwin->w_jumplist[0].fname);
 		    for (i = 0; i < idx; ++i)
 			curwin->w_jumplist[i] = curwin->w_jumplist[i + 1];