diff --git a/Source/cmGeneratorTarget.cxx b/Source/cmGeneratorTarget.cxx
index 1d8d2ddf4..4d335cdbb 100644
--- a/Source/cmGeneratorTarget.cxx
+++ b/Source/cmGeneratorTarget.cxx
@@ -328,7 +328,7 @@ void cmGeneratorTarget::AddObject(cmSourceFile const* sf,
 }
 
 //----------------------------------------------------------------------------
-void cmGeneratorTarget::AddExplicitObjectName(cmSourceFile* sf)
+void cmGeneratorTarget::AddExplicitObjectName(cmSourceFile const* sf)
 {
   this->ExplicitObjectName.insert(sf);
 }
diff --git a/Source/cmGeneratorTarget.h b/Source/cmGeneratorTarget.h
index e5ed27167..d1a0e0610 100644
--- a/Source/cmGeneratorTarget.h
+++ b/Source/cmGeneratorTarget.h
@@ -37,7 +37,7 @@ public:
 
   void AddObject(cmSourceFile const* sf, std::string const&name);
   bool HasExplicitObjectName(cmSourceFile const* file) const;
-  void AddExplicitObjectName(cmSourceFile* sf);
+  void AddExplicitObjectName(cmSourceFile const* sf);
 
   void GetResxSources(std::vector<cmSourceFile*>&) const;
   void GetIDLSources(std::vector<cmSourceFile*>&) const;