diff --git a/CHANGELOG.md b/CHANGELOG.md
index 03b1ba691..b40465d9f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## Unreleased
+
+### Fixed
+
+- Text `margin` arrays now map as documented TRBL `[top, right, bottom, left]` instead of LRBT (`lIns`/`tIns` were swapped)
+
 ## [4.0.1](https://github.com/gitbrent/PptxGenJS/releases/tag/v4.0.1) - 2025-06-25
 
 ### Fixed
diff --git a/demos/modules/demo_text.mjs b/demos/modules/demo_text.mjs
index 6f292055d..b30002571 100644
--- a/demos/modules/demo_text.mjs
+++ b/demos/modules/demo_text.mjs
@@ -59,6 +59,20 @@ function genSlide01(pptx) {
 		{ x: 10, y: 2.25, w: 3.0, h: 1.0, color: "FFFFFF", fill: { color: "C00000" }, valign: "bottom", align: "right", margin: 0 }
 	);
 
+	// TEST-CASE: text margin arrays are TRBL [top, right, bottom, left]
+	// Left inset should be large here (not top). Regression: LRBT mapping swapped ends.
+	slide.addText("margin:[5,5,5,40]\n(left=40pt)", {
+		x: 10,
+		y: 3.35,
+		w: 3.0,
+		h: 0.9,
+		color: "363636",
+		fill: { color: "F1F1F1" },
+		fontSize: 12,
+		valign: "middle",
+		margin: [5, 5, 5, 40],
+	});
+
 	slide.addText("^ (50%/50%)", { x: "50%", y: "50%", w: 2 });
 
 	slide.addText("Plain x/y coords", { x: 10, y: 4.35, w: 3 });
@@ -202,6 +216,7 @@ function genSlide02(pptx) {
 	});
 
 	// 4: Line-Spacing (bullets)
+	// TEST-CASE: margin [0,0,0,10] = left 10pt (TRBL), not top
 	slide.addText("Line-Spacing (bullets):", { x: 7.0, y: 5.6, w: "40%", h: 0.3, margin: 0, color: pptx.colors.ACCENT1 });
 	slide.addText([{ text: "lineSpacing\n35pt", options: { fontSize: 24, bullet: true, color: "99ABCC", lineSpacing: 35 } }], {
 		x: 7.0,
diff --git a/src/gen-xml.ts b/src/gen-xml.ts
index f1e3ecd9f..1f1f77819 100644
--- a/src/gen-xml.ts
+++ b/src/gen-xml.ts
@@ -391,13 +391,13 @@ function slideObjectToXml (slide: PresSlide | SlideLayout): string {
 				// Lines can have zero cy, but text should not
 				if (!slideItemObj.options.line && cy === 0) cy = EMU * 0.3
 
-				// Margin/Padding/Inset for textboxes
+				// Margin/Padding/Inset for textboxes (TRBL: [top, right, bottom, left])
 				if (!slideItemObj.options._bodyProp) slideItemObj.options._bodyProp = {}
 				if (slideItemObj.options.margin && Array.isArray(slideItemObj.options.margin)) {
-					slideItemObj.options._bodyProp.lIns = valToPts(slideItemObj.options.margin[0] || 0)
+					slideItemObj.options._bodyProp.tIns = valToPts(slideItemObj.options.margin[0] || 0)
 					slideItemObj.options._bodyProp.rIns = valToPts(slideItemObj.options.margin[1] || 0)
 					slideItemObj.options._bodyProp.bIns = valToPts(slideItemObj.options.margin[2] || 0)
-					slideItemObj.options._bodyProp.tIns = valToPts(slideItemObj.options.margin[3] || 0)
+					slideItemObj.options._bodyProp.lIns = valToPts(slideItemObj.options.margin[3] || 0)
 				} else if (typeof slideItemObj.options.margin === 'number') {
 					slideItemObj.options._bodyProp.lIns = valToPts(slideItemObj.options.margin)
 					slideItemObj.options._bodyProp.rIns = valToPts(slideItemObj.options.margin)