diff --git a/app/internal_packages/ui-dark/package.json b/app/internal_packages/ui-dark/package.json
index 8ba48ee7f..0637baa61 100644
--- a/app/internal_packages/ui-dark/package.json
+++ b/app/internal_packages/ui-dark/package.json
@@ -5,7 +5,6 @@
   "version": "0.1.0",
   "description": "The Dark N1 Client Theme",
   "license": "GPL-3.0",
-  "styleSheets": ["email-frame"],
   "engines": {
     "mailspring": "*"
   },
diff --git a/app/internal_packages/ui-darkside/index.less b/app/internal_packages/ui-darkside/index.less
deleted file mode 100644
index e7f1d3d76..000000000
--- a/app/internal_packages/ui-darkside/index.less
+++ /dev/null
@@ -1,14 +0,0 @@
-@import "styles/darkside-variables";
-@import "styles/darkside-sidebar";
-@import "styles/darkside-toolbars";
-@import "styles/darkside-window-controls";
-@import "styles/darkside-threadlist";
-@import "styles/darkside-inputs";
-@import "styles/darkside-thread-icons";
-@import "styles/darkside-swiping";
-@import "styles/darkside-labels";
-@import "styles/darkside-message-list";
-@import "styles/darkside-composer";
-@import "styles/darkside-preferences";
-@import "styles/darkside-notifications";
-@import "styles/darkside-drafts";
diff --git a/app/internal_packages/ui-darkside/styles/index.less b/app/internal_packages/ui-darkside/styles/index.less
new file mode 100644
index 000000000..bdddec032
--- /dev/null
+++ b/app/internal_packages/ui-darkside/styles/index.less
@@ -0,0 +1,14 @@
+@import 'darkside-variables';
+@import 'darkside-sidebar';
+@import 'darkside-toolbars';
+@import 'darkside-window-controls';
+@import 'darkside-threadlist';
+@import 'darkside-inputs';
+@import 'darkside-thread-icons';
+@import 'darkside-swiping';
+@import 'darkside-labels';
+@import 'darkside-message-list';
+@import 'darkside-composer';
+@import 'darkside-preferences';
+@import 'darkside-notifications';
+@import 'darkside-drafts';
diff --git a/app/internal_packages/ui-less-is-more/index.less b/app/internal_packages/ui-less-is-more/index.less
deleted file mode 100644
index e69de29bb..000000000
diff --git a/app/internal_packages/ui-less-is-more/package.json b/app/internal_packages/ui-less-is-more/package.json
index 1cecbcaff..a5576bb40 100644
--- a/app/internal_packages/ui-less-is-more/package.json
+++ b/app/internal_packages/ui-less-is-more/package.json
@@ -1,13 +1,12 @@
 {
   "name": "less-is-more",
   "displayName": "Less Is More",
-  "theme": "ui-less-is-more",
+  "theme": "ui",
   "version": "1.0.7",
   "description": "A minimal approach to email in Mailspring",
   "license": "MIT",
   "engines": {
     "mailspring": "*"
   },
-  "styleSheets": ["less-is-more"],
   "private": true
 }
diff --git a/app/internal_packages/ui-less-is-more/styles/less-is-more.less b/app/internal_packages/ui-less-is-more/styles/index.less
similarity index 100%
rename from app/internal_packages/ui-less-is-more/styles/less-is-more.less
rename to app/internal_packages/ui-less-is-more/styles/index.less
diff --git a/app/internal_packages/ui-less-is-more/styles/theme-colors.less b/app/internal_packages/ui-less-is-more/styles/theme-colors.less
index ed351e097..f754deb78 100644
--- a/app/internal_packages/ui-less-is-more/styles/theme-colors.less
+++ b/app/internal_packages/ui-less-is-more/styles/theme-colors.less
@@ -1,4 +1,4 @@
-@import "less-is-more";
+@import 'index';
 
 @background-secondary: @less-background;
 @text-color: @less-text;
diff --git a/app/internal_packages/ui-taiga/package.json b/app/internal_packages/ui-taiga/package.json
index dbbd11a7e..88d3df255 100644
--- a/app/internal_packages/ui-taiga/package.json
+++ b/app/internal_packages/ui-taiga/package.json
@@ -8,6 +8,5 @@
   "engines": {
     "mailspring": "*"
   },
-  "styleSheets": ["controls", "email-frame", "sidebar", "threads", "notifications"],
   "private": true
 }
diff --git a/app/spec/fixtures/packages/theme-with-incomplete-ui-variables/package.json b/app/spec/fixtures/packages/theme-with-incomplete-ui-variables/package.json
index b62d9ab61..19419846a 100755
--- a/app/spec/fixtures/packages/theme-with-incomplete-ui-variables/package.json
+++ b/app/spec/fixtures/packages/theme-with-incomplete-ui-variables/package.json
@@ -1,4 +1,3 @@
 {
   "theme": "ui",
-  "styleSheets": ["editor.less"]
 }
diff --git a/app/spec/fixtures/packages/theme-with-package-file/package.json b/app/spec/fixtures/packages/theme-with-package-file/package.json
deleted file mode 100755
index 71ec9577a..000000000
--- a/app/spec/fixtures/packages/theme-with-package-file/package.json
+++ /dev/null
@@ -1,4 +0,0 @@
-{
-  "theme": "ui",
-  "styleSheets": ["first.css", "second.less", "last.css"]
-}
diff --git a/app/spec/fixtures/packages/theme-with-package-file/styles/first.css b/app/spec/fixtures/packages/theme-with-package-file/styles/first.css
deleted file mode 100755
index adfa4ea02..000000000
--- a/app/spec/fixtures/packages/theme-with-package-file/styles/first.css
+++ /dev/null
@@ -1,7 +0,0 @@
-nylas-theme-wrap {
-  padding-top: 101px;
-  padding-right: 101px;
-  padding-bottom: 101px;
-
-  color: red;
-}
diff --git a/app/spec/fixtures/packages/theme-with-package-file/styles/last.css b/app/spec/fixtures/packages/theme-with-package-file/styles/last.css
deleted file mode 100755
index e3d35f2b5..000000000
--- a/app/spec/fixtures/packages/theme-with-package-file/styles/last.css
+++ /dev/null
@@ -1,5 +0,0 @@
-nylas-theme-wrap {
-/*  padding-top: 103px;
-  padding-right: 103px;*/
-  padding-bottom: 103px;
-}
diff --git a/app/spec/fixtures/packages/theme-with-package-file/styles/second.less b/app/spec/fixtures/packages/theme-with-package-file/styles/second.less
deleted file mode 100755
index 2a415fad9..000000000
--- a/app/spec/fixtures/packages/theme-with-package-file/styles/second.less
+++ /dev/null
@@ -1,7 +0,0 @@
-@number: 102px;
-
-nylas-theme-wrap {
-/*  padding-top: 102px;*/
-  padding-right: @number;
-  padding-bottom: @number;
-}