diff --git a/.storybook/webpack.config.js b/.storybook/webpack.config.js
index 829742f..0acb91f 100644
--- a/.storybook/webpack.config.js
+++ b/.storybook/webpack.config.js
@@ -24,7 +24,7 @@ module.exports = {
 		},
 		{
 			test: /\.(gif|png|jpe?g|svg)$/i,
-			loader: 'file-loader', 
+			loader: 'file-loader',
 			options: {
 				paths: [
 					path.resolve( __dirname, './resolve-imports' )
@@ -42,6 +42,7 @@ module.exports = {
 				loader: 'less-loader',
 				options: {
 					relativeUrls: false,
+					strictUnits: true,
 					paths: [
 					 	path.resolve( __dirname, 'resolve-imports' )
 					]
diff --git a/variables.less b/variables.less
index 107f057..9d71df0 100644
--- a/variables.less
+++ b/variables.less
@@ -97,8 +97,8 @@
 @margin-start-portal-body: @margin-start-nav-main-body;
 
 // Navigation: Personal tools
-@background-position-nav-personal-icon: left ( 4 / @font-size-browser / @font-size-nav-personal );
-@background-size-nav-personal-icon: 14 / @font-size-browser / @font-size-nav-personal;
+@background-position-nav-personal-icon: left unit( 4 / @font-size-browser / @font-size-nav-personal, em );
+@background-size-nav-personal-icon: unit( 14 / @font-size-browser / @font-size-nav-personal, em );
 @top-personal-tools: 6px;
 @font-size-nav-personal: 0.75em;
 // Using `unit()` without second parameter to achieve a unitless output for `line-height`.
@@ -108,7 +108,7 @@
 @font-size-tabs: unit( 13 / @font-size-browser, em ); // Equals `0.8125em`.
 
 // Search
-@width-search-button: 24 / @font-size-browser / @font-size-search-input;
+@width-search-button: unit( 24 / @font-size-browser / @font-size-search-input, em );
 @font-size-search-input: unit( 13 / @font-size-browser, em ); // Equals `0.8125em`.
 
 // Z-indices