diff --git a/ext/gd/libgd/gd.c b/ext/gd/libgd/gd.c
index 5170f4f8c04..89c7dbdd585 100644
--- a/ext/gd/libgd/gd.c
+++ b/ext/gd/libgd/gd.c
@@ -1051,11 +1051,13 @@ void gdImageAABlend (gdImagePtr im)
 	}
 }
 
+static void _gdImageFilledHRectangle (gdImagePtr im, int x1, int y1, int x2, int y2, int color);
+
 static void gdImageHLine(gdImagePtr im, int y, int x1, int x2, int col)
 {
 	if (im->thick > 1) {
 		int thickhalf = im->thick >> 1;
-		gdImageFilledRectangle(im, x1, y - thickhalf, x2, y + im->thick - thickhalf - 1, col);
+		_gdImageFilledHRectangle(im, x1, y - thickhalf, x2, y + im->thick - thickhalf - 1, col);
 	} else {
 		if (x2 < x1) {
 			int t = x2;
@@ -2120,10 +2122,53 @@ void gdImageRectangle (gdImagePtr im, int x1, int y1, int x2, int y2, int color)
 	}
 }
 
-void gdImageFilledRectangle (gdImagePtr im, int x1, int y1, int x2, int y2, int color)
+static void _gdImageFilledHRectangle (gdImagePtr im, int x1, int y1, int x2, int y2, int color)
 {
 	int x, y;
 
+	if (x1 == x2 && y1 == y2) {
+		gdImageSetPixel(im, x1, y1, color);
+		return;
+	}
+
+	if (x1 > x2) {
+		x = x1;
+		x1 = x2;
+		x2 = x;
+	}
+
+	if (y1 > y2) {
+		y = y1;
+		y1 = y2;
+		y2 = y;
+	}
+
+	if (x1 < 0) {
+		x1 = 0;
+	}
+
+	if (x2 >= gdImageSX(im)) {
+		x2 = gdImageSX(im) - 1;
+	}
+
+	if (y1 < 0) {
+		y1 = 0;
+	}
+
+	if (y2 >= gdImageSY(im)) {
+		y2 = gdImageSY(im) - 1;
+	}
+
+	for (x = x1; (x <= x2); x++) {
+		for (y = y1; (y <= y2); y++) {
+			gdImageSetPixel (im, x, y, color);
+		}
+	}
+}
+
+static void _gdImageFilledVRectangle (gdImagePtr im, int x1, int y1, int x2, int y2, int color)
+{
+	int x, y;
 
 	if (x1 == x2 && y1 == y2) {
 		gdImageSetPixel(im, x1, y1, color);
@@ -2165,6 +2210,11 @@ void gdImageFilledRectangle (gdImagePtr im, int x1, int y1, int x2, int y2, int
 	}
 }
 
+void gdImageFilledRectangle (gdImagePtr im, int x1, int y1, int x2, int y2, int color)
+{
+	_gdImageFilledVRectangle(im, x1, y1, x2, y2, color);
+}
+
 void gdImageCopy (gdImagePtr dst, gdImagePtr src, int dstX, int dstY, int srcX, int srcY, int w, int h)
 {
 	int c;
diff --git a/ext/gd/tests/bug43475.phpt b/ext/gd/tests/bug43475.phpt
new file mode 100644
index 00000000000..b29b9800a58
--- /dev/null
+++ b/ext/gd/tests/bug43475.phpt
@@ -0,0 +1,59 @@
+--TEST--
+Bug #43475 (Thick styled lines have scrambled patterns)
+--SKIPIF--
+<?php
+	if (!extension_loaded('gd')) die("skip gd extension not available\n");
+?>
+--FILE--
+<?php
+require_once __DIR__ . '/similarity.inc';
+
+function setStyleAndThickness($im, $color, $thickness)
+{
+	$style = array();
+	$i = 0;
+	while ($i < 16 * $thickness) {
+		$style[$i++] = $color;
+	}
+	while ($i < 20 * $thickness) {
+		$style[$i++] = IMG_COLOR_TRANSPARENT;
+	}
+	while ($i < 28 * $thickness) {
+		$style[$i++] = $color;
+	}
+	while ($i < 32 * $thickness) {
+		$style[$i++] = IMG_COLOR_TRANSPARENT;
+	}
+	imagesetstyle($im, $style);
+	imagesetthickness($im, $thickness);
+}
+
+$im = imagecreate(800, 800);
+imagecolorallocate($im, 255, 255, 255);
+$black = imagecolorallocate($im, 0, 0, 0);
+
+setStyleAndThickness($im, $black, 1);
+imageline($im,  50, 250, 550, 250, IMG_COLOR_STYLED);
+imageline($im, 550, 250, 550, 750, IMG_COLOR_STYLED);
+imageline($im, 550, 750,  50, 250, IMG_COLOR_STYLED);
+
+setStyleAndThickness($im, $black, 2);
+imageline($im, 100, 200, 600, 200, IMG_COLOR_STYLED);
+imageline($im, 600, 200, 600, 700, IMG_COLOR_STYLED);
+imageline($im, 600, 700, 100, 200, IMG_COLOR_STYLED);
+
+setStyleAndThickness($im, $black, 4);
+imageline($im, 150, 150, 650, 150, IMG_COLOR_STYLED);
+imageline($im, 650, 150, 650, 650, IMG_COLOR_STYLED);
+imageline($im, 650, 650, 150, 150, IMG_COLOR_STYLED);
+
+setStyleAndThickness($im, $black, 6);
+imageline($im, 200, 100, 700, 100, IMG_COLOR_STYLED);
+imageline($im, 700, 100, 700, 600, IMG_COLOR_STYLED);
+imageline($im, 700, 600, 200, 100, IMG_COLOR_STYLED);
+
+$ex = imagecreatefrompng(__DIR__ . '/bug43475.png');
+var_dump(calc_image_dissimilarity($ex, $im) < 1e-5);
+?>
+--EXPECT--
+bool(true)
diff --git a/ext/gd/tests/bug43475.png b/ext/gd/tests/bug43475.png
new file mode 100644
index 00000000000..774270f63db
Binary files /dev/null and b/ext/gd/tests/bug43475.png differ