diff --git a/Source/kwsys/ProcessUNIX.c b/Source/kwsys/ProcessUNIX.c
index adadef15f3..9c66a44866 100644
--- a/Source/kwsys/ProcessUNIX.c
+++ b/Source/kwsys/ProcessUNIX.c
@@ -720,6 +720,14 @@ void kwsysProcess_Execute(kwsysProcess* cp)
     return;
     }
 
+  /* Make sure we have something to run.  */
+  if(cp->NumberOfCommands < 1)
+    {
+    strcpy(cp->ErrorMessage, "No command");
+    cp->State = kwsysProcess_State_Error;
+    return;
+    }
+
   /* Initialize the control structure for a new process.  */
   if(!kwsysProcessInitialize(cp))
     {
diff --git a/Source/kwsys/ProcessWin32.c b/Source/kwsys/ProcessWin32.c
index c5ea6db206..5aa4d8bf6e 100644
--- a/Source/kwsys/ProcessWin32.c
+++ b/Source/kwsys/ProcessWin32.c
@@ -987,6 +987,14 @@ void kwsysProcess_Execute(kwsysProcess* cp)
     return;
     }
 
+  /* Make sure we have something to run.  */
+  if(cp->NumberOfCommands < 1)
+    {
+    strcpy(cp->ErrorMessage, "No command");
+    cp->State = kwsysProcess_State_Error;
+    return;
+    }
+
   /* Initialize the control structure for a new process.  */
   if(!kwsysProcessInitialize(cp))
     {