diff --git a/WHATSNEW b/WHATSNEW
index 00de20e3e..0dddcbf00 100644
--- a/WHATSNEW
+++ b/WHATSNEW
@@ -254,6 +254,10 @@ Other changes:
    in verbose runs.
    Bugzilla Report 48836.
 
+ * StringUtils.parseHumanSizes() should turn parse failures into
+   BuildExceptions.
+   Bugzilla Report 48835.
+
 Changes from Ant 1.8.0 TO Ant 1.8.1 
 ===================================
 
diff --git a/src/main/org/apache/tools/ant/util/StringUtils.java b/src/main/org/apache/tools/ant/util/StringUtils.java
index 6fd84b25e..5887d9377 100644
--- a/src/main/org/apache/tools/ant/util/StringUtils.java
+++ b/src/main/org/apache/tools/ant/util/StringUtils.java
@@ -17,6 +17,8 @@
  */
 package org.apache.tools.ant.util;
 
+import org.apache.tools.ant.BuildException;
+
 import java.io.PrintWriter;
 import java.io.StringWriter;
 import java.util.Vector;
@@ -239,7 +241,11 @@ public final class StringUtils {
             }
             humanSize = humanSize.substring(0, humanSize.length() - trim);
         }
-        return factor * Long.parseLong(humanSize);
+        try {
+            return factor * Long.parseLong(humanSize);
+        } catch (NumberFormatException e) {
+            throw new BuildException("Failed to parse \"" + humanSize + "\"", e);
+        }
     }
 
     /**