diff --git a/layout.c b/layout.c
index bb1bbf8d..266d1f39 100644
--- a/layout.c
+++ b/layout.c
@@ -686,6 +686,8 @@ layout_split_pane(
 	case LAYOUT_LEFTRIGHT:
 		if (size < 0)
 			size2 = ((sx + 1) / 2) - 1;
+		else if (insert_before)
+			size2 = sx - size - 1;
 		else
 			size2 = size;
 		if (size2 < PANE_MINIMUM)
@@ -699,6 +701,8 @@ layout_split_pane(
 	case LAYOUT_TOPBOTTOM:
 		if (size < 0)
 			size2 = ((sy + 1) / 2) - 1;
+		else if (insert_before)
+			size2 = sy - size - 1;
 		else
 			size2 = size;
 		if (size2 < PANE_MINIMUM)