diff --git a/.github/workflows/actions.yml b/.github/workflows/actions.yml
index 1c5de1a14..10f5c09ae 100644
--- a/.github/workflows/actions.yml
+++ b/.github/workflows/actions.yml
@@ -210,6 +210,7 @@ jobs:
             -DENABLE_TESTS=OFF \
             -DENABLE_UTILS=${{ (needs.what-to-make.outputs.make-utils == 'true') && 'ON' || 'OFF' }} \
             -DENABLE_WEB=OFF \
+            -DENABLE_WERROR=ON \
             -DRUN_CLANG_TIDY=OFF
       - name: Make
         run: cmake --build obj --config RelWithDebInfo
@@ -284,6 +285,7 @@ jobs:
             -DENABLE_TESTS=OFF \
             -DENABLE_UTILS=${{ (needs.what-to-make.outputs.make-utils == 'true') && 'ON' || 'OFF' }} \
             -DENABLE_WEB=OFF \
+            -DENABLE_WERROR=ON \
             -DRUN_CLANG_TIDY=OFF
       - name: Make
         run: cmake --build obj --config RelWithDebInfo
@@ -375,6 +377,7 @@ jobs:
             -DENABLE_TESTS=ON `
             -DENABLE_UTILS=${{ (needs.what-to-make.outputs.make-dist == 'true' || needs.what-to-make.outputs.make-utils == 'true') && 'ON' || 'OFF' }} `
             -DENABLE_WEB=OFF `
+            -DENABLE_WERROR=ON `
             -DRUN_CLANG_TIDY=OFF
       - name: Make
         run: |
@@ -478,6 +481,7 @@ jobs:
             -DENABLE_TESTS=${{ (needs.what-to-make.outputs.make-tests == 'true') && 'ON' || 'OFF' }} \
             -DENABLE_UTILS=${{ (needs.what-to-make.outputs.make-utils == 'true') && 'ON' || 'OFF' }} \
             -DENABLE_WEB=OFF \
+            -DENABLE_WERROR=ON \
             -DRUN_CLANG_TIDY=OFF
       - name: Make
         run: cmake --build obj --config RelWithDebInfo
@@ -553,6 +557,7 @@ jobs:
             -DENABLE_TESTS=${{ (needs.what-to-make.outputs.make-tests == 'true') && 'ON' || 'OFF' }} \
             -DENABLE_UTILS=${{ (needs.what-to-make.outputs.make-utils == 'true') && 'ON' || 'OFF' }} \
             -DENABLE_WEB=OFF \
+            -DENABLE_WERROR=ON \
             -DRUN_CLANG_TIDY=OFF
       - name: Build
         run: cmake --build obj --config RelWithDebInfo
@@ -625,6 +630,7 @@ jobs:
             -DENABLE_TESTS=${{ (needs.what-to-make.outputs.make-tests == 'true') && 'ON' || 'OFF' }} \
             -DENABLE_UTILS=${{ (needs.what-to-make.outputs.make-utils == 'true') && 'ON' || 'OFF' }} \
             -DENABLE_WEB=OFF \
+            -DENABLE_WERROR=ON \
             -DRUN_CLANG_TIDY=OFF
       - name: Build
         run: cmake --build obj --config RelWithDebInfo
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 0267368e3..1bee0603b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -50,6 +50,7 @@ tr_auto_option(ENABLE_MAC           "Build Mac client" AUTO)
         option(ENABLE_TESTS         "Build unit tests" ON)
         option(ENABLE_LIGHTWEIGHT   "Optimize libtransmission for low-resource systems: smaller cache size, prefer unencrypted peer connections, etc." OFF)
         option(ENABLE_UTP           "Build µTP support" ON)
+        option(ENABLE_WERROR        "Treat warnings as errors" OFF)
         option(ENABLE_NLS           "Enable native language support" ON)
         option(INSTALL_DOC          "Build/install documentation" ON)
         option(INSTALL_LIB          "Install the library" OFF)
diff --git a/gtk/CMakeLists.txt b/gtk/CMakeLists.txt
index 634c05a9c..b8c57881f 100644
--- a/gtk/CMakeLists.txt
+++ b/gtk/CMakeLists.txt
@@ -1,6 +1,9 @@
 project(trgtk)
 
 add_compile_options(${C_WARNING_FLAGS})
+if(ENABLE_WERROR)
+    add_compile_options($<IF:$<CXX_COMPILER_ID:MSVC>,/WX,-Werror>)
+endif()
 
 execute_process(
     COMMAND
diff --git a/gtk/PathButton.cc b/gtk/PathButton.cc
index c2005e845..7c7e6d6df 100644
--- a/gtk/PathButton.cc
+++ b/gtk/PathButton.cc
@@ -41,9 +41,9 @@ private:
 #endif
 
 private:
+#if GTKMM_CHECK_VERSION(4, 0, 0)
     PathButton& widget_;
 
-#if GTKMM_CHECK_VERSION(4, 0, 0)
     Glib::Property<Gtk::FileChooser::Action> action_;
     Glib::Property<Glib::ustring> title_;
 
@@ -59,9 +59,9 @@ private:
 #endif
 };
 
-PathButton::Impl::Impl(PathButton& widget)
-    : widget_(widget)
+PathButton::Impl::Impl([[maybe_unused]] PathButton& widget)
 #if GTKMM_CHECK_VERSION(4, 0, 0)
+    : widget_(widget)
     , action_(widget, "action", Gtk::FileChooser::Action::OPEN)
     , title_(widget, "title", {})
     , image_(Gtk::make_managed<Gtk::Image>())