diff --git a/src/test/java/org/apache/commons/lang3/StringUtilsIsTest.java b/src/test/java/org/apache/commons/lang3/StringUtilsIsTest.java
index 2b3f33122..be85e75bf 100644
--- a/src/test/java/org/apache/commons/lang3/StringUtilsIsTest.java
+++ b/src/test/java/org/apache/commons/lang3/StringUtilsIsTest.java
@@ -166,6 +166,7 @@ public class StringUtilsIsTest extends AbstractLangTest {
         assertFalse(StringUtils.isWhitespace("a  "));
         assertFalse(StringUtils.isWhitespace("  a"));
         assertFalse(StringUtils.isWhitespace("aba"));
+        assertFalse(StringUtils.isWhitespace("a"));
         assertTrue(StringUtils.isWhitespace(StringUtilsTest.WHITESPACE));
         assertFalse(StringUtils.isWhitespace(StringUtilsTest.NON_WHITESPACE));
     }