diff --git a/src/main/org/apache/tools/ant/types/mappers/CutDirsMapper.java b/src/main/org/apache/tools/ant/types/mappers/CutDirsMapper.java
index ce8f39c13..932f3ec13 100644
--- a/src/main/org/apache/tools/ant/types/mappers/CutDirsMapper.java
+++ b/src/main/org/apache/tools/ant/types/mappers/CutDirsMapper.java
@@ -63,6 +63,9 @@ public class CutDirsMapper implements FileNameMapper {
             throw new BuildException("dirs must be set to a positive number");
         }
         final char fileSep = File.separatorChar;
+        if (sourceFileName == null) {
+            return null;
+        }
         final String fileSepCorrected =
             sourceFileName.replace('/', fileSep).replace('\\', fileSep);
         int nthMatch = fileSepCorrected.indexOf(fileSep);
diff --git a/src/main/org/apache/tools/ant/types/mappers/FilterMapper.java b/src/main/org/apache/tools/ant/types/mappers/FilterMapper.java
index 501da5000..9ef922e5f 100644
--- a/src/main/org/apache/tools/ant/types/mappers/FilterMapper.java
+++ b/src/main/org/apache/tools/ant/types/mappers/FilterMapper.java
@@ -63,6 +63,9 @@ public class FilterMapper extends FilterChain implements FileNameMapper {
      *          the filterchain returns an empty string.
      */
     public String[] mapFileName(String sourceFileName) {
+        if (sourceFileName == null) {
+            return null;
+        }
         try {
             Reader stringReader = new StringReader(sourceFileName);
             ChainReaderHelper helper = new ChainReaderHelper();
diff --git a/src/main/org/apache/tools/ant/util/FlatFileNameMapper.java b/src/main/org/apache/tools/ant/util/FlatFileNameMapper.java
index 420ccc6c9..04d58bed5 100644
--- a/src/main/org/apache/tools/ant/util/FlatFileNameMapper.java
+++ b/src/main/org/apache/tools/ant/util/FlatFileNameMapper.java
@@ -49,6 +49,7 @@ public class FlatFileNameMapper implements FileNameMapper {
      * @return the file name in a one-element array.
      */
     public String[] mapFileName(String sourceFileName) {
-        return new String[] {new java.io.File(sourceFileName).getName()};
+        return sourceFileName == null ? null
+            : new String[] {new java.io.File(sourceFileName).getName()};
     }
 }
diff --git a/src/main/org/apache/tools/ant/util/GlobPatternMapper.java b/src/main/org/apache/tools/ant/util/GlobPatternMapper.java
index ebba54ea2..a0f0ca987 100644
--- a/src/main/org/apache/tools/ant/util/GlobPatternMapper.java
+++ b/src/main/org/apache/tools/ant/util/GlobPatternMapper.java
@@ -154,6 +154,9 @@ public class GlobPatternMapper implements FileNameMapper {
      * @return a list of converted filenames
      */
     public String[] mapFileName(String sourceFileName) {
+        if (sourceFileName == null) {
+            return null;
+        }
         String modName = modifyName(sourceFileName);
         if (fromPrefix == null
             || (sourceFileName.length() < (prefixLength + postfixLength))
diff --git a/src/main/org/apache/tools/ant/util/RegexpPatternMapper.java b/src/main/org/apache/tools/ant/util/RegexpPatternMapper.java
index fa620d9ad..6a2f4b5c7 100644
--- a/src/main/org/apache/tools/ant/util/RegexpPatternMapper.java
+++ b/src/main/org/apache/tools/ant/util/RegexpPatternMapper.java
@@ -114,6 +114,9 @@ public class RegexpPatternMapper implements FileNameMapper {
      *         null if the to pattern did not match
      */
     public String[] mapFileName(String sourceFileName) {
+        if (sourceFileName == null) {
+            return null;
+        }
         if (handleDirSep) {
             if (sourceFileName.indexOf("\\") != -1) {
                 sourceFileName = sourceFileName.replace('\\', '/');