diff --git a/src/main/java/org/apache/commons/lang3/math/NumberUtils.java b/src/main/java/org/apache/commons/lang3/math/NumberUtils.java
index c00c5cf28..9eaf57d68 100644
--- a/src/main/java/org/apache/commons/lang3/math/NumberUtils.java
+++ b/src/main/java/org/apache/commons/lang3/math/NumberUtils.java
@@ -1489,7 +1489,7 @@ public static boolean isParsable(final String str) {
             return false;
         }
         if( StringUtils.startsWith( str, "-" ) ) {
-            return isDigits( StringUtils.replaceOnce( StringUtils.substring( str, 1 ), ".", StringUtils.EMPTY ) );
+            return isDigits( StringUtils.replaceOnce( str.substring(1), ".", StringUtils.EMPTY ) );
         } else {
             return isDigits( StringUtils.replaceOnce( str, ".", StringUtils.EMPTY ) );
         }