diff --git a/Source/cmAddLibraryCommand.cxx b/Source/cmAddLibraryCommand.cxx
index 575dd04f2..2bc65ceba 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;
diff --git a/Source/cmAddLibraryCommand.h b/Source/cmAddLibraryCommand.h
index ad23ffc5b..6cad681a9 100644
--- a/Source/cmAddLibraryCommand.h
+++ b/Source/cmAddLibraryCommand.h
@@ -100,7 +100,7 @@ public:
       "\n"
       "The add_library command can also create IMPORTED library "
       "targets using this signature:\n"
-      "  add_library(<name> <SHARED|STATIC|MODULE> IMPORTED)\n"
+      "  add_library(<name> <SHARED|STATIC|MODULE|UNKNOWN> IMPORTED)\n"
       "An IMPORTED library target references a library file located "
       "outside the project.  "
       "No rules are generated to build it.  "
diff --git a/Source/cmComputeLinkDepends.cxx b/Source/cmComputeLinkDepends.cxx
index 177ec5877..df329a67f 100644
--- a/Source/cmComputeLinkDepends.cxx
+++ b/Source/cmComputeLinkDepends.cxx
@@ -890,6 +890,14 @@ void cmComputeLinkDepends::CheckWrongConfigItem(std::string const& item)
     }
 }
 
+//----------------------------------------------------------------------------
+static bool cmComputeLinkDependsNotStatic(cmTarget* tgt)
+{
+  return (tgt &&
+          tgt->GetType() != cmTarget::STATIC_LIBRARY &&
+          tgt->GetType() != cmTarget::UNKNOWN_LIBRARY);
+}
+
 //----------------------------------------------------------------------------
 void cmComputeLinkDepends::PreserveOriginalEntries()
 {
@@ -901,7 +909,7 @@ void cmComputeLinkDepends::PreserveOriginalEntries()
         out != this->FinalLinkOrder.end())
     {
     cmTarget* tgt = this->EntryList[*in].Target;
-    if(tgt && tgt->GetType() != cmTarget::STATIC_LIBRARY)
+    if(cmComputeLinkDependsNotStatic(tgt))
       {
       // Skip input items known to not be static libraries.
       ++in;
@@ -924,7 +932,7 @@ void cmComputeLinkDepends::PreserveOriginalEntries()
   while(in != this->OriginalEntries.end())
     {
     cmTarget* tgt = this->EntryList[*in].Target;
-    if(tgt && tgt->GetType() != cmTarget::STATIC_LIBRARY)
+    if(cmComputeLinkDependsNotStatic(tgt))
       {
       // Skip input items known to not be static libraries.
       ++in;
diff --git a/Source/cmComputeLinkInformation.cxx b/Source/cmComputeLinkInformation.cxx
index 6e0f10bf7..0b02ae12f 100644
--- a/Source/cmComputeLinkInformation.cxx
+++ b/Source/cmComputeLinkInformation.cxx
@@ -581,10 +581,7 @@ void cmComputeLinkInformation::AddItem(std::string const& item, cmTarget* tgt)
     return;
     }
 
-  if(tgt && (tgt->GetType() == cmTarget::STATIC_LIBRARY ||
-             tgt->GetType() == cmTarget::SHARED_LIBRARY ||
-             tgt->GetType() == cmTarget::MODULE_LIBRARY ||
-             impexe))
+  if(tgt && tgt->IsLinkable())
     {
     // This is a CMake target.  Ask the target for its real name.
     if(impexe && this->LoaderFlag)
@@ -1555,6 +1552,14 @@ void
 cmComputeLinkInformation::AddLibraryRuntimeInfo(std::string const& fullPath,
                                                 cmTarget* target)
 {
+  // Libraries with unknown type must be handled using just the file
+  // on disk.
+  if(target->GetType() == cmTarget::UNKNOWN_LIBRARY)
+    {
+    this->AddLibraryRuntimeInfo(fullPath);
+    return;
+    }
+
   // Skip targets that are not shared libraries (modules cannot be linked).
   if(target->GetType() != cmTarget::SHARED_LIBRARY)
     {
diff --git a/Source/cmLocalGenerator.cxx b/Source/cmLocalGenerator.cxx
index 064cfb5ac..4bf183943 100644
--- a/Source/cmLocalGenerator.cxx
+++ b/Source/cmLocalGenerator.cxx
@@ -1706,6 +1706,7 @@ std::string cmLocalGenerator::GetRealDependency(const char* inName,
       case cmTarget::STATIC_LIBRARY:
       case cmTarget::SHARED_LIBRARY:
       case cmTarget::MODULE_LIBRARY:
+      case cmTarget::UNKNOWN_LIBRARY:
         {
         // Get the location of the target's output file and depend on it.
         if(const char* location = target->GetLocation(config))
diff --git a/Source/cmTarget.cxx b/Source/cmTarget.cxx
index caa534f38..296e93df3 100644
--- a/Source/cmTarget.cxx
+++ b/Source/cmTarget.cxx
@@ -30,7 +30,8 @@
 const char* cmTarget::TargetTypeNames[] = {
   "EXECUTABLE", "STATIC_LIBRARY",
   "SHARED_LIBRARY", "MODULE_LIBRARY", "UTILITY", "GLOBAL_TARGET",
-  "INSTALL_FILES", "INSTALL_PROGRAMS", "INSTALL_DIRECTORY"
+  "INSTALL_FILES", "INSTALL_PROGRAMS", "INSTALL_DIRECTORY",
+  "UNKNOWN_LIBRARY"
 };
 
 //----------------------------------------------------------------------------
@@ -277,6 +278,7 @@ void cmTarget::DefineProperties(cmake *cm)
      "For frameworks on OS X this is the location of the library file "
      "symlink just inside the framework folder.  "
      "For DLLs this is the location of the \".dll\" part of the library.  "
+     "For UNKNOWN libraries this is the location of the file to be linked.  "
      "Ignored for non-imported targets.");
 
   cm->DefineProperty
@@ -786,6 +788,16 @@ bool cmTarget::IsExecutableWithExports()
           this->GetPropertyAsBool("ENABLE_EXPORTS"));
 }
 
+//----------------------------------------------------------------------------
+bool cmTarget::IsLinkable()
+{
+  return (this->GetType() == cmTarget::STATIC_LIBRARY ||
+          this->GetType() == cmTarget::SHARED_LIBRARY ||
+          this->GetType() == cmTarget::MODULE_LIBRARY ||
+          this->GetType() == cmTarget::UNKNOWN_LIBRARY ||
+          this->IsExecutableWithExports());
+}
+
 //----------------------------------------------------------------------------
 bool cmTarget::IsFrameworkOnApple()
 {
@@ -1860,7 +1872,8 @@ const char *cmTarget::GetProperty(const char* prop,
   if(this->GetType() == cmTarget::EXECUTABLE ||
      this->GetType() == cmTarget::STATIC_LIBRARY ||
      this->GetType() == cmTarget::SHARED_LIBRARY ||
-     this->GetType() == cmTarget::MODULE_LIBRARY)
+     this->GetType() == cmTarget::MODULE_LIBRARY ||
+     this->GetType() == cmTarget::UNKNOWN_LIBRARY)
     {
     if(!this->IsImported() && strcmp(prop,"LOCATION") == 0)
       {
@@ -1957,6 +1970,9 @@ const char *cmTarget::GetProperty(const char* prop,
       case cmTarget::INSTALL_DIRECTORY:
         return "INSTALL_DIRECTORY";
         // break; /* unreachable */
+      case cmTarget::UNKNOWN_LIBRARY:
+        return "UNKNOWN_LIBRARY";
+        // break; /* unreachable */
       }
     return 0;
     }
diff --git a/Source/cmTarget.h b/Source/cmTarget.h
index 7141e4184..07004bed7 100644
--- a/Source/cmTarget.h
+++ b/Source/cmTarget.h
@@ -80,7 +80,8 @@ public:
   cmTarget();
   enum TargetType { EXECUTABLE, STATIC_LIBRARY,
                     SHARED_LIBRARY, MODULE_LIBRARY, UTILITY, GLOBAL_TARGET,
-                    INSTALL_FILES, INSTALL_PROGRAMS, INSTALL_DIRECTORY};
+                    INSTALL_FILES, INSTALL_PROGRAMS, INSTALL_DIRECTORY,
+                    UNKNOWN_LIBRARY};
   static const char* TargetTypeNames[];
   enum CustomCommandType { PRE_BUILD, PRE_LINK, POST_BUILD };
 
@@ -393,6 +394,9 @@ public:
       enabled.  */
   bool IsExecutableWithExports();
 
+  /** Return whether this target may be used to link another target.  */
+  bool IsLinkable();
+
   /** Return whether this target is a shared library Framework on
       Apple.  */
   bool IsFrameworkOnApple();
diff --git a/Tests/SimpleInstall/CMakeLists.txt b/Tests/SimpleInstall/CMakeLists.txt
index 34914b6a3..c204e6410 100644
--- a/Tests/SimpleInstall/CMakeLists.txt
+++ b/Tests/SimpleInstall/CMakeLists.txt
@@ -66,9 +66,13 @@ IF(STAGE2)
     PATHS ${LIBPATHS}
     DOC "Fourth library")
 
+  # Test importing a library found on disk.
+  ADD_LIBRARY(lib_test4 UNKNOWN IMPORTED)
+  SET_PROPERTY(TARGET lib_test4 PROPERTY IMPORTED_LOCATION ${TEST4_LIBRARY})
+
   INCLUDE_DIRECTORIES(${CMAKE_INSTALL_PREFIX}/MyTest/include)
   ADD_EXECUTABLE (SimpleInstExeS2 inst2.cxx foo.c foo.h)
-  TARGET_LINK_LIBRARIES(SimpleInstExeS2 ${TEST1_LIBRARY} ${TEST2_LIBRARY} ${TEST4_LIBRARY})
+  TARGET_LINK_LIBRARIES(SimpleInstExeS2 ${TEST1_LIBRARY} ${TEST2_LIBRARY} lib_test4)
   SET(install_target SimpleInstExeS2)
 
   IF("${TEST1_LIBRARY}" MATCHES "static")
diff --git a/Tests/SimpleInstallS2/CMakeLists.txt b/Tests/SimpleInstallS2/CMakeLists.txt
index 34914b6a3..c204e6410 100644
--- a/Tests/SimpleInstallS2/CMakeLists.txt
+++ b/Tests/SimpleInstallS2/CMakeLists.txt
@@ -66,9 +66,13 @@ IF(STAGE2)
     PATHS ${LIBPATHS}
     DOC "Fourth library")
 
+  # Test importing a library found on disk.
+  ADD_LIBRARY(lib_test4 UNKNOWN IMPORTED)
+  SET_PROPERTY(TARGET lib_test4 PROPERTY IMPORTED_LOCATION ${TEST4_LIBRARY})
+
   INCLUDE_DIRECTORIES(${CMAKE_INSTALL_PREFIX}/MyTest/include)
   ADD_EXECUTABLE (SimpleInstExeS2 inst2.cxx foo.c foo.h)
-  TARGET_LINK_LIBRARIES(SimpleInstExeS2 ${TEST1_LIBRARY} ${TEST2_LIBRARY} ${TEST4_LIBRARY})
+  TARGET_LINK_LIBRARIES(SimpleInstExeS2 ${TEST1_LIBRARY} ${TEST2_LIBRARY} lib_test4)
   SET(install_target SimpleInstExeS2)
 
   IF("${TEST1_LIBRARY}" MATCHES "static")