diff --git a/src/main/java/org/codehaus/mojo/exec/ExecMojo.java b/src/main/java/org/codehaus/mojo/exec/ExecMojo.java
index 439d875a..c997889b 100644
--- a/src/main/java/org/codehaus/mojo/exec/ExecMojo.java
+++ b/src/main/java/org/codehaus/mojo/exec/ExecMojo.java
@@ -676,6 +676,10 @@ else if ( isLongModulePathArgument( specialArg ) || isLongClassPathArgument( spe
             {
                 specialArg = (String) argument;
             }
+            else if (argument == null)
+            {
+                commandArguments.add( "" );
+            }
             else
             {
                 commandArguments.add( (String) argument );