diff --git a/src/plugins/boxShadow.js b/src/plugins/boxShadow.js
index abfd9097e..5309236aa 100644
--- a/src/plugins/boxShadow.js
+++ b/src/plugins/boxShadow.js
@@ -1,4 +1,5 @@
 import _ from 'lodash'
+import prefixNegativeModifiers from '../util/prefixNegativeModifiers'
 
 export default function() {
   return function({ addUtilities, e, theme, variants }) {
@@ -6,7 +7,7 @@ export default function() {
       _.map(theme('boxShadow'), (value, modifier) => {
         const className = modifier === 'default' ? 'shadow' : `shadow-${modifier}`
         return [
-          `.${e(className)}`,
+          `.${e(prefixNegativeModifiers('shadow', modifier))}`,
           {
             'box-shadow': value,
           },
diff --git a/src/plugins/letterSpacing.js b/src/plugins/letterSpacing.js
index 7efeaa38f..bdcd2e5bd 100644
--- a/src/plugins/letterSpacing.js
+++ b/src/plugins/letterSpacing.js
@@ -1,11 +1,12 @@
 import _ from 'lodash'
+import prefixNegativeModifiers from '../util/prefixNegativeModifiers'
 
 export default function() {
   return function({ addUtilities, theme, variants, e }) {
     const utilities = _.fromPairs(
       _.map(theme('letterSpacing'), (value, modifier) => {
         return [
-          `.${e(`tracking-${modifier}`)}`,
+          `.${e(prefixNegativeModifiers('tracking', modifier))}`,
           {
             'letter-spacing': value,
           },
diff --git a/src/util/prefixNegativeModifiers.js b/src/util/prefixNegativeModifiers.js
index 3b0ab62c2..80c932f3f 100644
--- a/src/util/prefixNegativeModifiers.js
+++ b/src/util/prefixNegativeModifiers.js
@@ -1,5 +1,9 @@
 import _ from 'lodash'
 
 export default function prefixNegativeModifiers(base, modifier) {
-  return _.startsWith(modifier, '-') ? `-${base}-${modifier.slice(1)}` : `${base}-${modifier}`
+  return modifier === '-'
+    ? `-${base}`
+    : _.startsWith(modifier, '-')
+      ? `-${base}-${modifier.slice(1)}`
+      : `${base}-${modifier}`
 }