1 files changed, 16 insertions, 0 deletions
diff --git a/Source/cmAddLibraryCommand.cxx b/Source/cmAddLibraryCommand.cxx
index 575dd04..2bc65ce 100644
--- a/Source/cmAddLibraryCommand.cxx
+++ b/Source/cmAddLibraryCommand.cxx
@@ -68,6 +68,12 @@ bool cmAddLibraryCommand
       type = cmTarget::MODULE_LIBRARY;
       haveSpecifiedType = true;
       }
+    else if(libType == "UNKNOWN")
+      {
+      ++s;
+      type = cmTarget::UNKNOWN_LIBRARY;
+      haveSpecifiedType = true;
+      }
     else if(*s == "EXCLUDE_FROM_ALL")
       {
       ++s;
@@ -127,6 +133,16 @@ bool cmAddLibraryCommand
     return true;
     }
 
+  // A non-imported target may not have UNKNOWN type.
+  if(type == cmTarget::UNKNOWN_LIBRARY)
+    {
+    this->Makefile->IssueMessage(
+      cmake::FATAL_ERROR,
+      "The UNKNOWN library type may be used only for IMPORTED libraries."
+      );
+    return true;
+    }
+
   // Enforce name uniqueness.
   {
   std::string msg;