diff --git a/Source/cmGeneratorExpression.cxx b/Source/cmGeneratorExpression.cxx
index 7ea58fa..3f59129 100644
--- a/Source/cmGeneratorExpression.cxx
+++ b/Source/cmGeneratorExpression.cxx
@@ -393,7 +393,7 @@ bool cmGeneratorExpression::IsValidTargetName(const std::string &input)
   cmsys::RegularExpression targetNameValidator;
   // The ':' is supported to allow use with IMPORTED targets. At least
   // Qt 4 and 5 IMPORTED targets use ':' as the namespace delimiter.
-  targetNameValidator.compile("^[A-Za-z0-9_.:-]+$");
+  targetNameValidator.compile("^[A-Za-z0-9_.:+-]+$");
 
   return targetNameValidator.find(input.c_str());
 }