diff --git a/Source/cmAddCustomCommandCommand.cxx b/Source/cmAddCustomCommandCommand.cxx
index ac1f4eb21..138d96f8e 100644
--- a/Source/cmAddCustomCommandCommand.cxx
+++ b/Source/cmAddCustomCommandCommand.cxx
@@ -171,6 +171,16 @@ bool cmAddCustomCommandCommand::InitialPass(std::vector<std::string> const& args
     return false;
     }
 
+  std::string::size_type pos = output.find_first_of("#<>");
+  if(pos != output.npos)
+    {
+    cmOStringStream msg;
+    msg << "called with OUTPUT containing a \"" << output[pos]
+        << "\".  This character is not allowed.";
+    this->SetError(msg.str().c_str());
+    return false;
+    }
+
   // Choose which mode of the command to use.
   if(source.empty() && output.empty())
     {
diff --git a/Source/cmAddCustomTargetCommand.cxx b/Source/cmAddCustomTargetCommand.cxx
index ceb5241e0..02ae1615d 100644
--- a/Source/cmAddCustomTargetCommand.cxx
+++ b/Source/cmAddCustomTargetCommand.cxx
@@ -90,6 +90,16 @@ bool cmAddCustomTargetCommand::InitialPass(std::vector<std::string> const& args)
       }
     }
 
+  std::string::size_type pos = args[0].find_first_of("#<>");
+  if(pos != args[0].npos)
+    {
+    cmOStringStream msg;
+    msg << "called with target name containing a \"" << args[0][pos]
+        << "\".  This character is not allowed.";
+    this->SetError(msg.str().c_str());
+    return false;
+    }
+
   // Store the last command line finished.
   if(!currentLine.empty())
     {