diff --git a/src/render/stacking-context.ts b/src/render/stacking-context.ts
index 32497e3..27787b6 100644
--- a/src/render/stacking-context.ts
+++ b/src/render/stacking-context.ts
@@ -115,7 +115,7 @@ const parseStackTree = (
} else if (order > 0) {
let index = 0;
parentStack.positiveZIndex.some((current, i) => {
- if (order > current.element.container.styles.zIndex.order) {
+ if (order >= current.element.container.styles.zIndex.order) {
index = i + 1;
return false;
} else if (index > 0) {
diff --git a/tests/reftests/zindex/z-index20.html b/tests/reftests/zindex/z-index20.html
new file mode 100644
index 0000000..7bfdfe6
--- /dev/null
+++ b/tests/reftests/zindex/z-index20.html
@@ -0,0 +1,41 @@
+
+
+
+
+ z-index20
+
+
+
+
+
+
+