diff --git a/CMakeLists.txt b/CMakeLists.txt
index 6998326b6..746626c28 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -19,7 +19,8 @@ if(MSVC)
   set(CMAKE_EXE_LINKER_FLAGS_RELWITHDEBINFO "/DEBUG /RELEASE /LTCG /OPT:REF /OPT:ICF /INCREMENTAL:NO /DEBUGTYPE:cv,fixup")
 
 else()
-  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++14 -Wno-multichar -fno-exceptions -Wno-narrowing -Wno-nullability-completeness")
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}\
+  -std=c++14 -Wno-multichar -fno-exceptions -Wno-narrowing -Wno-nullability-completeness -Werror=return-type")
 
   if(APPLE)
     set(CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS_RELEASE} -flto=thin")
diff --git a/Runtime/GuiSys/CGuiTextSupport.cpp b/Runtime/GuiSys/CGuiTextSupport.cpp
index 2fb7fe947..030ecc1d4 100644
--- a/Runtime/GuiSys/CGuiTextSupport.cpp
+++ b/Runtime/GuiSys/CGuiTextSupport.cpp
@@ -165,6 +165,8 @@ bool CGuiTextSupport::CheckAndRebuildRenderBuffer()
     {
         zeus::CVector2i extent(x34_extentX, x38_extentY);
     }
+
+    return true;
 }
 
 void CGuiTextSupport::Render() const
diff --git a/Runtime/MP1/CFrontEndUI.cpp b/Runtime/MP1/CFrontEndUI.cpp
index 31f79a894..505232900 100644
--- a/Runtime/MP1/CFrontEndUI.cpp
+++ b/Runtime/MP1/CFrontEndUI.cpp
@@ -546,7 +546,7 @@ void CFrontEndUI::SGBASupportFrame::SetTableColors(CGuiTableGroup* tbgp) const
 CFrontEndUI::SGBASupportFrame::EAction
 CFrontEndUI::SGBASupportFrame::ProcessUserInput(const CFinalInput& input, CSaveUI* sui)
 {
-
+    return EAction::Zero;
 }
 
 void CFrontEndUI::SGBASupportFrame::Draw() const
@@ -756,7 +756,7 @@ CFrontEndUI::SOptionsFrontEndFrame::SOptionsFrontEndFrame()
 
 bool CFrontEndUI::SOptionsFrontEndFrame::ProcessUserInput(const CFinalInput& input, CSaveUI* sui)
 {
-
+    return true;
 }
 
 void CFrontEndUI::SOptionsFrontEndFrame::Draw() const