Improve exception message
diff --git a/src/main/java/org/apache/commons/fileupload/MultipartStream.java b/src/main/java/org/apache/commons/fileupload/MultipartStream.java
index ee60a3d..38d57ff 100644
--- a/src/main/java/org/apache/commons/fileupload/MultipartStream.java
+++ b/src/main/java/org/apache/commons/fileupload/MultipartStream.java
@@ -507,7 +507,7 @@
             throws IllegalBoundaryException {
         if (boundary.length != boundaryLength - BOUNDARY_PREFIX.length) {
             throw new IllegalBoundaryException(
-            "The length of a boundary token can not be changed");
+            "The length of a boundary token cannot be changed");
         }
         System.arraycopy(boundary, 0, this.boundary, BOUNDARY_PREFIX.length,
                 boundary.length);