diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index cdee2f6..506a4c8 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -27,13 +27,13 @@ jobs:
     - uses: actions/checkout@v1
     - name: make test
       run: |
-        make -j2 config=sanitize test
+        make -j2 config=sanitize werror=1 test
     - name: make test w/flags
       run: |
-        make -j2 config=sanitize flags=true test
+        make -j2 config=sanitize werror=1 flags=true test
     - name: make cli
       run: |
-         make -j2 config=sanitize luau luau-analyze # match config with tests to improve build time
+         make -j2 config=sanitize werror=1 luau luau-analyze # match config with tests to improve build time
          ./luau tests/conformance/assert.lua
          ./luau-analyze tests/conformance/assert.lua
 
@@ -45,7 +45,7 @@ jobs:
     steps:
     - uses: actions/checkout@v1
     - name: cmake configure
-      run: cmake . -A ${{matrix.arch}}
+      run: cmake . -A ${{matrix.arch}} -DLUAU_WERROR=ON
     - name: cmake test
       shell: bash # necessary for fail-fast
       run: |
diff --git a/Analysis/src/TypeInfer.cpp b/Analysis/src/TypeInfer.cpp
index a6696ef..96b7992 100644
--- a/Analysis/src/TypeInfer.cpp
+++ b/Analysis/src/TypeInfer.cpp
@@ -1509,7 +1509,7 @@ ExprResult<TypeId> TypeChecker::checkExpr(const ScopePtr& scope, const AstExprVa
         std::vector<TypeId> types = flatten(varargPack).first;
         return {!types.empty() ? types[0] : nilType};
     }
-    else if (auto ftp = get<FreeTypePack>(varargPack))
+    else if (get<FreeTypePack>(varargPack))
     {
         TypeId head = freshType(scope);
         TypePackId tail = freshTypePack(scope);
@@ -1539,7 +1539,7 @@ ExprResult<TypeId> TypeChecker::checkExpr(const ScopePtr& scope, const AstExprCa
     {
         return {pack->head.empty() ? nilType : pack->head[0], std::move(result.predicates)};
     }
-    else if (auto ftp = get<Unifiable::Free>(retPack))
+    else if (get<Unifiable::Free>(retPack))
     {
         TypeId head = freshType(scope);
         TypePackId pack = addTypePack(TypePackVar{TypePack{{head}, freshTypePack(scope)}});
diff --git a/Analysis/src/TypeVar.cpp b/Analysis/src/TypeVar.cpp
index cd447ca..4ee5cb8 100644
--- a/Analysis/src/TypeVar.cpp
+++ b/Analysis/src/TypeVar.cpp
@@ -293,7 +293,7 @@ bool isGeneric(TypeId ty)
 bool maybeGeneric(TypeId ty)
 {
     ty = follow(ty);
-    if (auto ftv = get<FreeTypeVar>(ty))
+    if (get<FreeTypeVar>(ty))
         return true;
     else if (auto ttv = get<TableTypeVar>(ty))
     {
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 36014a9..d9ef9c0 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -9,6 +9,7 @@ project(Luau LANGUAGES CXX)
 
 option(LUAU_BUILD_CLI "Build CLI" ON)
 option(LUAU_BUILD_TESTS "Build tests" ON)
+option(LUAU_WERROR "Warnings as errors" OFF)
 
 add_library(Luau.Ast STATIC)
 add_library(Luau.Compiler STATIC)
@@ -57,11 +58,18 @@ set(LUAU_OPTIONS)
 
 if(MSVC)
     list(APPEND LUAU_OPTIONS /D_CRT_SECURE_NO_WARNINGS) # We need to use the portable CRT functions.
-    list(APPEND LUAU_OPTIONS /WX) # Warnings are errors
     list(APPEND LUAU_OPTIONS /MP) # Distribute single project compilation across multiple cores
 else()
     list(APPEND LUAU_OPTIONS -Wall) # All warnings
-    list(APPEND LUAU_OPTIONS -Werror) # Warnings are errors
+endif()
+
+# Enabled in CI; we should be warning free on our main compiler versions but don't guarantee being warning free everywhere
+if(LUAU_WERROR)
+    if(MSVC)
+        list(APPEND LUAU_OPTIONS /WX) # Warnings are errors
+    else()
+        list(APPEND LUAU_OPTIONS -Werror) # Warnings are errors
+    endif()
 endif()
 
 target_compile_options(Luau.Ast PRIVATE ${LUAU_OPTIONS})
diff --git a/Makefile b/Makefile
index ffe4309..ce461af 100644
--- a/Makefile
+++ b/Makefile
@@ -46,14 +46,20 @@ endif
 OBJECTS=$(AST_OBJECTS) $(COMPILER_OBJECTS) $(ANALYSIS_OBJECTS) $(VM_OBJECTS) $(TESTS_OBJECTS) $(CLI_OBJECTS) $(FUZZ_OBJECTS)
 
 # common flags
-CXXFLAGS=-g -Wall -Werror
+CXXFLAGS=-g -Wall
 LDFLAGS=
 
-# temporary, for older gcc versions as they treat var in `if (type var = val)` as unused
+# some gcc versions treat var in `if (type var = val)` as unused
+# some gcc versions treat variables used in constexpr if blocks as unused
 ifeq ($(findstring g++,$(shell $(CXX) --version)),g++)
 	CXXFLAGS+=-Wno-unused
 endif
 
+# enabled in CI; we should be warning free on our main compiler versions but don't guarantee being warning free everywhere
+ifneq ($(werror),)
+	CXXFLAGS+=-Werror
+endif
+
 # configuration-specific flags
 ifeq ($(config),release)
 	CXXFLAGS+=-O2 -DNDEBUG