diff --git a/src/main/org/apache/tools/ant/taskdefs/rmic/DefaultRmicAdapter.java b/src/main/org/apache/tools/ant/taskdefs/rmic/DefaultRmicAdapter.java
index d32386725..ae6b16611 100644
--- a/src/main/org/apache/tools/ant/taskdefs/rmic/DefaultRmicAdapter.java
+++ b/src/main/org/apache/tools/ant/taskdefs/rmic/DefaultRmicAdapter.java
@@ -29,6 +29,7 @@ import org.apache.tools.ant.taskdefs.Rmic;
 import org.apache.tools.ant.types.Commandline;
 import org.apache.tools.ant.types.Path;
 import org.apache.tools.ant.util.FileNameMapper;
+import org.apache.tools.ant.util.StringUtils;
 
 /**
  * This is the default implementation for the RmicAdapter interface.
@@ -365,7 +366,7 @@ public abstract class DefaultRmicAdapter implements RmicAdapter {
             }
 
             // we know that name.endsWith(".class")
-            String base = name.substring(0, name.length() - ".class".length());
+            String base = StringUtils.removeSuffix(name, ".class");
 
             String classname = base.replace(File.separatorChar, '.');
             if (attributes.getVerify()
diff --git a/src/main/org/apache/tools/ant/types/optional/depend/ClassfileSet.java b/src/main/org/apache/tools/ant/types/optional/depend/ClassfileSet.java
index fb5cb90e2..6cc873b3f 100644
--- a/src/main/org/apache/tools/ant/types/optional/depend/ClassfileSet.java
+++ b/src/main/org/apache/tools/ant/types/optional/depend/ClassfileSet.java
@@ -22,6 +22,7 @@ import java.util.Enumeration;
 import org.apache.tools.ant.Project;
 import org.apache.tools.ant.DirectoryScanner;
 import org.apache.tools.ant.types.FileSet;
+import org.apache.tools.ant.util.StringUtils;
 
 /**
  * A ClassfileSet is a FileSet that enlists all classes that depend on a
@@ -125,9 +126,7 @@ public class ClassfileSet extends FileSet {
             String[] files = additionalScanner.getIncludedFiles();
             for (int i = 0; i < files.length; ++i) {
                 if (files[i].endsWith(".class")) {
-                    String classFilePath
-                        = files[i].substring(
-                            0, files[i].length() - ".class".length());
+                    String classFilePath = StringUtils.removeSuffix(files[i], ".class");
                     String className
                         = classFilePath.replace('/', '.').replace('\\', '.');
                     allRootClasses.addElement(className);