diff --git a/CHANGELOG.md b/CHANGELOG.md
index 44473e6ebbc..d77b4c1ef67 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,8 @@
 ## [`master`](https://github.com/elastic/eui/tree/master)
 
-No public interface changes since `10.4.0`
+**Bug fixes**
+
+- Fixed Firefox flash of unstyled select dropdown ([#1927](https://github.com/elastic/eui/pull/1927))
 
 ## [`10.4.0`](https://github.com/elastic/eui/tree/v10.4.0)
 
diff --git a/src/components/form/_mixins.scss b/src/components/form/_mixins.scss
index d64597fa2aa..472e4b63062 100644
--- a/src/components/form/_mixins.scss
+++ b/src/components/form/_mixins.scss
@@ -93,9 +93,16 @@
 
   transition:
     box-shadow $euiAnimSpeedFast ease-in,
-    background-color $euiAnimSpeedFast ease-in,
     background-image $euiAnimSpeedFast ease-in,
-    background-size $euiAnimSpeedFast ease-in;
+    background-size $euiAnimSpeedFast ease-in,
+    background-color $euiAnimSpeedFast ease-in;
+
+  // Fixes bug in Firefox where adding a transition to the background-color
+  // caused a flash of differently styled dropdown.
+  @supports (-moz-appearance: none) { // sass-lint:disable-line no-vendor-prefixes
+    // List *must* be in the same order as the above.
+    transition-property: box-shadow, background-image, background-size;
+  }
 }
 
 @mixin euiFormControlFocusStyle($borderOnly: false) {