diff --git a/Source/cmGeneratorTarget.cxx b/Source/cmGeneratorTarget.cxx
index 4d335cdbb..bde60b834 100644
--- a/Source/cmGeneratorTarget.cxx
+++ b/Source/cmGeneratorTarget.cxx
@@ -241,7 +241,7 @@ const char *cmGeneratorTarget::GetProperty(const std::string& prop) const
 
 //----------------------------------------------------------------------------
 std::vector<cmSourceFile*> const*
-cmGeneratorTarget::GetSourceDepends(cmSourceFile* sf) const
+cmGeneratorTarget::GetSourceDepends(cmSourceFile const* sf) const
 {
   SourceEntriesType::const_iterator i = this->SourceEntries.find(sf);
   if(i != this->SourceEntries.end())
diff --git a/Source/cmGeneratorTarget.h b/Source/cmGeneratorTarget.h
index d1a0e0610..1c4276cb1 100644
--- a/Source/cmGeneratorTarget.h
+++ b/Source/cmGeneratorTarget.h
@@ -87,7 +87,8 @@ public:
   void LookupObjectLibraries();
 
   /** Get sources that must be built before the given source.  */
-  std::vector<cmSourceFile*> const* GetSourceDepends(cmSourceFile* sf) const;
+  std::vector<cmSourceFile*> const*
+  GetSourceDepends(cmSourceFile const* sf) const;
 
   /**
    * Flags for a given source file as used in this target. Typically assigned
@@ -121,7 +122,7 @@ public:
 private:
   friend class cmTargetTraceDependencies;
   struct SourceEntry { std::vector<cmSourceFile*> Depends; };
-  typedef std::map<cmSourceFile*, SourceEntry> SourceEntriesType;
+  typedef std::map<cmSourceFile const*, SourceEntry> SourceEntriesType;
   SourceEntriesType SourceEntries;
 
   std::map<cmSourceFile const*, std::string> Objects;