diff --git a/vaadin-split-layout-flow-parent/vaadin-split-layout-flow/src/main/java/com/vaadin/flow/component/splitlayout/SplitLayout.java b/vaadin-split-layout-flow-parent/vaadin-split-layout-flow/src/main/java/com/vaadin/flow/component/splitlayout/SplitLayout.java
index 2bbe4eefe8f..06b59253508 100644
--- a/vaadin-split-layout-flow-parent/vaadin-split-layout-flow/src/main/java/com/vaadin/flow/component/splitlayout/SplitLayout.java
+++ b/vaadin-split-layout-flow-parent/vaadin-split-layout-flow/src/main/java/com/vaadin/flow/component/splitlayout/SplitLayout.java
@@ -284,6 +284,11 @@ public Component getSecondaryComponent() {
      * of the component and in vertical mode this is the height. The given value
      * will automatically be clamped to the range [0, 100].
      *
+     * Note that when using vertical orientation, this method only works if the
+     * split layout has an explicit height, either as an absolute value or as
+     * percentage. When using a percentage value, ensure that ancestors have an
+     * explicit height as well.
+     *
      * @param position
      *            the relative position of the splitter, in percentages
      */