diff --git a/src/themes/BaseTheme.ts b/src/themes/BaseTheme.ts
index 3c346b8c..ba970073 100644
--- a/src/themes/BaseTheme.ts
+++ b/src/themes/BaseTheme.ts
@@ -1,4 +1,5 @@
 // import {ThemeOptions} from "@mui/material/styles";
+import { shouldSkipGeneratingVar as defaultShouldSkipGeneratingVar } from "@mui/material/styles";
 import { ImageColourSchemeSwitchType } from "../components/controls/ImageColourSchemeSwitch";
 
 // Make additions to theme, so that anything can be available throughout the app
@@ -20,6 +21,9 @@ declare module "@mui/material/styles" {
 const BaseThemeOptions /* : ThemeOptions */ = {
   cssVariables: {
     colorSchemeSelector: "class",
+    // `logos` holds raw image sources (e.g. SVG data URIs), not CSS values, so skip var generation for it.
+    shouldSkipGeneratingVar: (keys: string[]) =>
+      keys[0] === "logos" || defaultShouldSkipGeneratingVar(keys),
   },
   typography: {
     fontSize: 14,
diff --git a/src/themes/DiamondDSTheme.ts b/src/themes/DiamondDSTheme.ts
index 8545ca22..57dd67e3 100644
--- a/src/themes/DiamondDSTheme.ts
+++ b/src/themes/DiamondDSTheme.ts
@@ -24,7 +24,10 @@ import "../styles/diamondDS/DiamondDSTypography.css";
 
 // Enables `theme.vars` typings for MUI CSS variable themes.
 import type {} from "@mui/material/themeCssVarsAugmentation";
-import { extendTheme } from "@mui/material/styles";
+import {
+  extendTheme,
+  shouldSkipGeneratingVar as defaultShouldSkipGeneratingVar,
+} from "@mui/material/styles";
 import type {
   CSSObject,
   Overlays,
@@ -734,6 +737,10 @@ const DiamondDSTheme = extendTheme({
    */
   colorSchemeSelector: '[data-mode="%s"]',
 
+  // `logos` holds raw image sources (e.g. SVG data URIs), not CSS values, so skip var generation for it.
+  shouldSkipGeneratingVar: (keys) =>
+    keys[0] === "logos" || defaultShouldSkipGeneratingVar(keys),
+
   colorSchemes: {
     light: {
       palette: createDiamondPalette("light"),