diff --git a/src/main/java/org/codehaus/mojo/exec/ExecMojo.java b/src/main/java/org/codehaus/mojo/exec/ExecMojo.java
index 533ed430..3b1494e1 100644
--- a/src/main/java/org/codehaus/mojo/exec/ExecMojo.java
+++ b/src/main/java/org/codehaus/mojo/exec/ExecMojo.java
@@ -564,6 +564,10 @@ else if ( isLongModulePathArgument( specialArg ) || isLongClassPathArgument( spe
             {
                 specialArg = (String) argument;
             }
+            else if (argument == null)
+            {
+                commandArguments.add( "" );
+            }
             else
             {
                 commandArguments.add( (String) argument );