diff --git a/crates/typst/src/visualize/color.rs b/crates/typst/src/visualize/color.rs
index 185e990b7..17f4b5a43 100644
--- a/crates/typst/src/visualize/color.rs
+++ b/crates/typst/src/visualize/color.rs
@@ -1191,7 +1191,7 @@ impl Color {
                 Color::Hsv(Hsv::new(RgbHue::from_degrees(m[0]), m[1], m[2], m[3]))
             }
             ColorSpace::Cmyk => Color::Cmyk(Cmyk::new(m[0], m[1], m[2], m[3])),
-            ColorSpace::D65Gray => Color::Luma(Luma::new(m[0], m[1])),
+            ColorSpace::D65Gray => Color::Luma(Luma::new(m[0], m[3])),
         })
     }
 
diff --git a/tests/ref/issue-color-mix-luma.png b/tests/ref/issue-color-mix-luma.png
new file mode 100644
index 000000000..957168926
Binary files /dev/null and b/tests/ref/issue-color-mix-luma.png differ
diff --git a/tests/suite/visualize/color.typ b/tests/suite/visualize/color.typ
index 332594615..da93cb4e2 100644
--- a/tests/suite/visualize/color.typ
+++ b/tests/suite/visualize/color.typ
@@ -329,3 +329,7 @@
 #color.hsl(blue) \
 #color.hsv(blue) \
 #luma(blue)
+
+--- issue-color-mix-luma ---
+// When mixing luma colors, we accidentally used the wrong component.
+#rect(fill: gradient.linear(black, silver, space: luma))