diff --git a/NEWS.md b/NEWS.md
index 1c82a69637..10a4869519 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,5 +1,10 @@
 # ggplot2 (development version)
 
+### Bug fixes
+
+* Fixed regression where `draw_key_rect()` stopped using `fill` colours 
+  (@mitchelloharawild, #6609).
+
 # ggplot2 4.0.0
 
 ## User facing
diff --git a/R/legend-draw.R b/R/legend-draw.R
index 25aedae0f7..621cde0aa2 100644
--- a/R/legend-draw.R
+++ b/R/legend-draw.R
@@ -54,7 +54,7 @@ draw_key_abline <- function(data, params, size) {
 #' @export
 #' @rdname draw_key
 draw_key_rect <- function(data, params, size) {
-  colour <- if (is.na(data$fill %||% NA)) data$colour
+  colour <- if (is.na(data$fill %||% NA)) data$colour else data$fill
   rectGrob(gp = gg_par(
     col = NA,
     fill = fill_alpha(colour %||% "grey20", data$alpha),
diff --git a/tests/testthat/_snaps/legend-draw/all-legend-keys.svg b/tests/testthat/_snaps/legend-draw/all-legend-keys.svg
index e535bebe99..c1ea77a335 100644
--- a/tests/testthat/_snaps/legend-draw/all-legend-keys.svg
+++ b/tests/testthat/_snaps/legend-draw/all-legend-keys.svg
@@ -23,7 +23,7 @@
 <text x='268.75' y='252.10' text-anchor='middle' style='font-size: 8.00px; font-family: sans;' textLength='21.35px' lengthAdjust='spacingAndGlyphs'>abline</text>
 <line x1='260.11' y1='273.83' x2='277.39' y2='256.55' style='stroke-width: 1.07; stroke-linecap: butt;' />
 <text x='268.75' y='312.13' text-anchor='middle' style='font-size: 8.00px; font-family: sans;' textLength='13.34px' lengthAdjust='spacingAndGlyphs'>rect</text>
-<rect x='260.11' y='316.57' width='17.28' height='17.28' style='stroke-width: 0.75; stroke: none; fill: #333333;' />
+<rect x='260.11' y='316.57' width='17.28' height='17.28' style='stroke-width: 0.75; stroke: none; fill: #595959;' />
 <text x='268.75' y='372.15' text-anchor='middle' style='font-size: 8.00px; font-family: sans;' textLength='28.03px' lengthAdjust='spacingAndGlyphs'>polygon</text>
 <rect x='260.82' y='377.31' width='15.86' height='15.86' style='stroke-width: 1.07; stroke: none; stroke-linecap: butt; stroke-linejoin: miter; fill: #333333;' />
 <text x='314.37' y='192.07' text-anchor='middle' style='font-size: 8.00px; font-family: sans;' textLength='19.13px' lengthAdjust='spacingAndGlyphs'>blank</text>