diff --git a/.internal/createCaseFirst.js b/.internal/createCaseFirst.js
index 029097a2f..2d4cfee74 100644
--- a/.internal/createCaseFirst.js
+++ b/.internal/createCaseFirst.js
@@ -11,6 +11,10 @@ import stringToArray from './stringToArray.js'
  */
 function createCaseFirst(methodName) {
   return (string) => {
+    if (!string) {
+      return ''
+    }
+
     const strSymbols = hasUnicode(string)
       ? stringToArray(string)
       : undefined
diff --git a/camelCase.js b/camelCase.js
index 596f37bf7..9882da6f2 100644
--- a/camelCase.js
+++ b/camelCase.js
@@ -1,5 +1,6 @@
 import upperFirst from './upperFirst.js'
 import words from './words.js'
+import toString from './toString.js'
 
 /**
  * Converts `string` to [camel case](https://en.wikipedia.org/wiki/CamelCase).
@@ -21,7 +22,7 @@ import words from './words.js'
  * // => 'fooBar'
  */
 const camelCase = (string) => (
-  words(`${string}`.replace(/['\u2019]/g, '')).reduce((result, word, index) => {
+  words(toString(string).replace(/['\u2019]/g, '')).reduce((result, word, index) => {
     word = word.toLowerCase()
     return result + (index ? upperFirst(word) : word)
   }, '')
diff --git a/capitalize.js b/capitalize.js
index 5b889d15c..2ad2ffed9 100644
--- a/capitalize.js
+++ b/capitalize.js
@@ -1,4 +1,5 @@
 import upperFirst from './upperFirst.js'
+import toString from './toString.js'
 
 /**
  * Converts the first character of `string` to upper case and the remaining
@@ -13,7 +14,7 @@ import upperFirst from './upperFirst.js'
  * capitalize('FRED')
  * // => 'Fred'
  */
-const capitalize = (string) =>  upperFirst(string.toLowerCase())
+const capitalize = (string) => upperFirst(toString(string).toLowerCase())
 
 
 export default capitalize
diff --git a/escape.js b/escape.js
index fa2ed605a..eda499a1c 100644
--- a/escape.js
+++ b/escape.js
@@ -41,7 +41,7 @@ const reHasUnescapedHtml = RegExp(reUnescapedHtml.source)
 function escape(string) {
   return (string && reHasUnescapedHtml.test(string))
     ? string.replace(reUnescapedHtml, (chr) => htmlEscapes[chr])
-    : string
+    : (string || '')
 }
 
 export default escape
diff --git a/kebabCase.js b/kebabCase.js
index 61b6898ca..bc436b949 100644
--- a/kebabCase.js
+++ b/kebabCase.js
@@ -1,4 +1,5 @@
 import words from './words.js'
+import toString from './toString.js'
 
 /**
  * Converts `string` to
@@ -21,7 +22,7 @@ import words from './words.js'
  * // => 'foo-bar'
  */
 const kebabCase = (string) => (
-  words(`${string}`.replace(/['\u2019]/g, '')).reduce((result, word, index) => (
+  words(toString(string).replace(/['\u2019]/g, '')).reduce((result, word, index) => (
     result + (index ? '-' : '') + word.toLowerCase()
   ), '')
 )
diff --git a/lowerCase.js b/lowerCase.js
index e460e5143..3da8966cf 100644
--- a/lowerCase.js
+++ b/lowerCase.js
@@ -1,4 +1,5 @@
 import words from './words.js'
+import toString from './toString.js'
 
 const reQuotes = /['\u2019]/g
 
@@ -22,7 +23,7 @@ const reQuotes = /['\u2019]/g
  * // => 'foo bar'
  */
 const lowerCase = (string) => (
-  words(`${string}`.replace(reQuotes, '')).reduce((result, word, index) => (
+  words(toString(string).replace(reQuotes, '')).reduce((result, word, index) => (
     result + (index ? ' ' : '') + word.toLowerCase()
   ), '')
 )
diff --git a/pad.js b/pad.js
index e37e4def8..3cfd9131b 100644
--- a/pad.js
+++ b/pad.js
@@ -25,7 +25,7 @@ import stringSize from './.internal/stringSize.js'
 function pad(string, length, chars) {
   const strLength = length ? stringSize(string) : 0
   if (!length || strLength >= length) {
-    return string
+    return (string || '')
   }
   const mid = (length - strLength) / 2
   return (
diff --git a/padEnd.js b/padEnd.js
index 3234c194a..0fe4ab188 100644
--- a/padEnd.js
+++ b/padEnd.js
@@ -26,7 +26,7 @@ function padEnd(string, length, chars) {
   const strLength = length ? stringSize(string) : 0
   return (length && strLength < length)
     ? (string + createPadding(length - strLength, chars))
-    : string
+    : (string || '')
 }
 
 export default padEnd
diff --git a/padStart.js b/padStart.js
index a4271b74f..025708384 100644
--- a/padStart.js
+++ b/padStart.js
@@ -26,7 +26,7 @@ function padStart(string, length, chars) {
   const strLength = length ? stringSize(string) : 0
   return (length && strLength < length)
     ? (createPadding(length - strLength, chars) + string)
-    : string
+    : (string || '')
 }
 
 export default padStart
diff --git a/snakeCase.js b/snakeCase.js
index 2599e9f56..8ddde6e41 100644
--- a/snakeCase.js
+++ b/snakeCase.js
@@ -1,4 +1,5 @@
 import words from './words.js'
+import toString from './toString.js'
 
 /**
  * Converts `string` to
@@ -24,7 +25,7 @@ import words from './words.js'
  * // => 'foo_2_bar'
  */
 const snakeCase = (string) => (
-  words(`${string}`.replace(/['\u2019]/g, '')).reduce((result, word, index) => (
+  words(toString(string).replace(/['\u2019]/g, '')).reduce((result, word, index) => (
     result + (index ? '_' : '') + word.toLowerCase()
   ), '')
 )
diff --git a/test/Strings-category-methods.js b/test/Strings-category-methods.js
deleted file mode 100644
index 9e391a56e..000000000
--- a/test/Strings-category-methods.js
+++ /dev/null
@@ -1,43 +0,0 @@
-import assert from 'assert';
-import lodashStable from 'lodash';
-import { _, stubString } from './utils.js';
-
-describe('"Strings" category methods', function() {
-  var stringMethods = [
-    'camelCase',
-    'capitalize',
-    'escape',
-    'kebabCase',
-    'lowerCase',
-    'lowerFirst',
-    'pad',
-    'padEnd',
-    'padStart',
-    'repeat',
-    'snakeCase',
-    'toLower',
-    'toUpper',
-    'trim',
-    'trimEnd',
-    'trimStart',
-    'truncate',
-    'unescape',
-    'upperCase',
-    'upperFirst'
-  ];
-
-  lodashStable.each(stringMethods, function(methodName) {
-    var func = _[methodName];
-
-    it('`_.' + methodName + '` should return an empty string for empty values', function() {
-      var values = [, null, undefined, ''],
-          expected = lodashStable.map(values, stubString);
-
-      var actual = lodashStable.map(values, function(value, index) {
-        return index ? func(value) : func();
-      });
-
-      assert.deepStrictEqual(actual, expected);
-    });
-  });
-});
diff --git a/test/Strings-category-methods.test.js b/test/Strings-category-methods.test.js
new file mode 100644
index 000000000..781a050ef
--- /dev/null
+++ b/test/Strings-category-methods.test.js
@@ -0,0 +1,83 @@
+import assert from 'assert';
+import lodashStable from 'lodash';
+import { stubString } from './utils.js';
+
+import camelCase from '../camelCase.js';
+import capitalize from '../capitalize.js';
+import escape from '../escape.js';
+import kebabCase from '../kebabCase.js';
+import lowerCase from '../lowerCase.js';
+import lowerFirst from '../lowerFirst.js';
+import pad from '../pad.js';
+import padEnd from '../padEnd.js';
+import padStart from '../padStart.js';
+import repeat from '../repeat.js';
+import snakeCase from '../snakeCase.js';
+import trim from '../trim.js';
+import trimStart from '../trimStart.js';
+import trimEnd from '../trimEnd.js';
+import truncate from '../truncate.js';
+import unescape from '../unescape.js';
+import upperCase from '../upperCase.js';
+import upperFirst from '../upperFirst';
+
+
+const methods = {
+  camelCase,
+  capitalize,
+  escape,
+  kebabCase,
+  lowerCase,
+  lowerFirst,
+  pad,
+  padEnd,
+  padStart,
+  repeat,
+  snakeCase,
+  trim,
+  trimStart,
+  trimEnd,
+  truncate,
+  unescape,
+  upperCase,
+  upperFirst
+}
+
+
+describe('"Strings" category methods', function() {
+  var stringMethods = [
+    'camelCase',
+    'capitalize',
+    'escape',
+    'kebabCase',
+    'lowerCase',
+    'lowerFirst',
+    'pad',
+    'padEnd',
+    'padStart',
+    'repeat',
+    'snakeCase',    
+    'trim',
+    'trimEnd',
+    'trimStart',
+    'truncate',
+    'unescape',
+    'upperCase',
+    'upperFirst'
+  ];
+
+  lodashStable.each(stringMethods, function(methodName) {
+    var func = methods[methodName];
+
+    it('`_.' + methodName + '` should return an empty string for empty values', function() {
+      var values = [, null, undefined, ''],
+          expected = lodashStable.map(values, stubString);
+
+      var actual = lodashStable.map(values, function(value, index) {
+        return index ? func(value) : func();
+      });
+
+      assert.deepStrictEqual(actual, expected);
+    });
+  });
+});
diff --git a/trim.js b/trim.js
index c79ead74c..b7ac73171 100644
--- a/trim.js
+++ b/trim.js
@@ -25,7 +25,7 @@ function trim(string, chars) {
     return string.trim()
   }
   if (!string || !chars) {
-    return string
+    return (string || '')
   }
   const strSymbols = stringToArray(string)
   const chrSymbols = stringToArray(chars)
diff --git a/trimEnd.js b/trimEnd.js
index caba219cf..b802521ba 100644
--- a/trimEnd.js
+++ b/trimEnd.js
@@ -26,7 +26,7 @@ function trimEnd(string, chars) {
     return string[methodName]()
   }
   if (!string || !chars) {
-    return string
+    return (string || '')
   }
   const strSymbols = stringToArray(string)
   const end = charsEndIndex(strSymbols, stringToArray(chars)) + 1
diff --git a/trimStart.js b/trimStart.js
index 2d232a888..6138a88e8 100644
--- a/trimStart.js
+++ b/trimStart.js
@@ -26,7 +26,7 @@ function trimStart(string, chars) {
     return string[methodName]()
   }
   if (!string || !chars) {
-    return string
+    return (string || '')
   }
   const strSymbols = stringToArray(string)
   const start = charsStartIndex(strSymbols, stringToArray(chars))
diff --git a/truncate.js b/truncate.js
index de0eef11f..f3a928cdc 100644
--- a/truncate.js
+++ b/truncate.js
@@ -5,6 +5,7 @@ import isObject from './isObject.js'
 import isRegExp from './isRegExp.js'
 import stringSize from './.internal/stringSize.js'
 import stringToArray from './.internal/stringToArray.js'
+import toString from './toString.js'
 
 /** Used as default options for `truncate`. */
 const DEFAULT_TRUNC_LENGTH = 30
@@ -59,6 +60,9 @@ function truncate(string, options) {
     length = 'length' in options ? options.length : length
     omission = 'omission' in options ? baseToString(options.omission) : omission
   }
+
+  string = toString(string)
+
   let strSymbols
   let strLength = string.length
   if (hasUnicode(string)) {
diff --git a/unescape.js b/unescape.js
index 9644f395c..e05c73608 100644
--- a/unescape.js
+++ b/unescape.js
@@ -32,7 +32,7 @@ const reHasEscapedHtml = RegExp(reEscapedHtml.source)
 function unescape(string) {
   return (string && reHasEscapedHtml.test(string))
     ? string.replace(reEscapedHtml, (entity) => htmlUnescapes[entity])
-    : string
+    : (string || '')
 }
 
 export default unescape
diff --git a/upperCase.js b/upperCase.js
index 68839526e..db14da836 100644
--- a/upperCase.js
+++ b/upperCase.js
@@ -1,4 +1,5 @@
 import words from './words.js'
+import toString from './toString.js'
 
 /**
  * Converts `string`, as space separated words, to upper case.
@@ -20,7 +21,7 @@ import words from './words.js'
  * // => 'FOO BAR'
  */
 const upperCase = (string) => (
-  words(`${string}`.replace(/['\u2019]/g, '')).reduce((result, word, index) => (
+  words(toString(string).replace(/['\u2019]/g, '')).reduce((result, word, index) => (
     result + (index ? ' ' : '') + word.toUpperCase()
   ), '')
 )