diff --git a/Source/cmExecProgramCommand.cxx b/Source/cmExecProgramCommand.cxx
index 378fe27f8..6ff22e950 100644
--- a/Source/cmExecProgramCommand.cxx
+++ b/Source/cmExecProgramCommand.cxx
@@ -111,7 +111,7 @@ bool cmExecProgramCommand::InitialPass(std::vector<std::string> const& args)
     {    
     std::string::size_type first = output.find_first_not_of(" \n\t\r");
     std::string::size_type last = output.find_last_not_of(" \n\t\r");
-    std::string coutput = std::string(output, first, last);
+    std::string coutput = std::string(output, first, last-first+1);
     m_Makefile->AddDefinition(output_variable.c_str(), coutput.c_str());
     }