diff --git a/CHANGES b/CHANGES
index c1b5a8ce2..078ac0e9c 100644
--- a/CHANGES
+++ b/CHANGES
@@ -24,6 +24,7 @@ Bugfixes:
  - DS: Fix exposed CPU frequencies and audio timing
  - DS Audio: Fix audio sampling slightly too quickly
  - Feature: Fix resizing GIF buffer (fixes mgba.io/i/695)
+ - DS GX: Retain translucent polygon ID when drawing opaque fragments (fixes mgba.io/i/661)
 Misc:
  - DS: Set boot complete bit in RAM on boot (fixes mgba.io/i/576, mgba.io/i/580, mgba.io/i/586)
  - DS Memory: Ensure DS9 I/O is 8-byte aligned
diff --git a/src/ds/gx/software.c b/src/ds/gx/software.c
index e50d8f9e8..9730f8f63 100644
--- a/src/ds/gx/software.c
+++ b/src/ds/gx/software.c
@@ -645,7 +645,8 @@ static void _drawSpan(struct DSGXSoftwareRenderer* softwareRenderer, struct DSGX
 			if (a == 0x1F) {
 				depth[x] = span->ep[0].coord[softwareRenderer->sort];
 				scanline[x] = color;
-				stencil[x] = s & 0x3F00;
+				stencil[x] &= 0x00FF;
+				stencil[x] |= s & 0x3F00;
 			} else if (a) {
 				// TODO: Disable alpha?
 				if (b) {