diff --git a/Source/cmVisualStudioSlnData.cxx b/Source/cmVisualStudioSlnData.cxx
index 8ed0ab8b93..4b6754eaa2 100644
--- a/Source/cmVisualStudioSlnData.cxx
+++ b/Source/cmVisualStudioSlnData.cxx
@@ -20,7 +20,7 @@ std::string cmSlnProjectEntry::GetProjectConfiguration(
   return projectConfigurationMap[solutionConfiguration];
 }
 
-const cm::optional<cmSlnProjectEntry> cmSlnData::GetProjectByGUID(
+cm::optional<cmSlnProjectEntry> cmSlnData::GetProjectByGUID(
   const std::string& projectGUID) const
 {
   auto it(ProjectsByGUID.find(projectGUID));
@@ -30,7 +30,7 @@ const cm::optional<cmSlnProjectEntry> cmSlnData::GetProjectByGUID(
   return cm::nullopt;
 }
 
-const cm::optional<cmSlnProjectEntry> cmSlnData::GetProjectByName(
+cm::optional<cmSlnProjectEntry> cmSlnData::GetProjectByName(
   const std::string& projectName) const
 {
   auto it(ProjectNameIndex.find(projectName));
diff --git a/Source/cmVisualStudioSlnData.h b/Source/cmVisualStudioSlnData.h
index 3188635024..5f03895947 100644
--- a/Source/cmVisualStudioSlnData.h
+++ b/Source/cmVisualStudioSlnData.h
@@ -56,10 +56,10 @@ public:
     minimumVisualStudioVersion = version;
   }
 
-  const cm::optional<cmSlnProjectEntry> GetProjectByGUID(
+  cm::optional<cmSlnProjectEntry> GetProjectByGUID(
     const std::string& projectGUID) const;
 
-  const cm::optional<cmSlnProjectEntry> GetProjectByName(
+  cm::optional<cmSlnProjectEntry> GetProjectByName(
     const std::string& projectName) const;
 
   std::vector<cmSlnProjectEntry> GetProjects() const;