diff --git a/src/db/db/dbPolygonGenerators.h b/src/db/db/dbPolygonGenerators.h
index e76c3cd87..a4127d59a 100644
--- a/src/db/db/dbPolygonGenerators.h
+++ b/src/db/db/dbPolygonGenerators.h
@@ -124,6 +124,11 @@ public:
    */
   virtual void put (const db::Edge &e);
 
+  /**
+   *  @brief Implementation of the EdgeSink interface
+   */
+  virtual void put (const db::Edge & /*e*/, int /*tag*/) { }
+
   /**
    *  @brief Sets the way how holes are resolved dynamically
    *
@@ -261,6 +266,11 @@ public:
    */
   virtual void put (const db::Edge &e);
 
+  /**
+   *  @brief Implementation of the EdgeSink interface
+   */
+  virtual void put (const db::Edge & /*e*/, int /*tag*/) { }
+
 private:
   db::Coord m_y;
   PolygonSink *mp_psink;
diff --git a/src/klayout.pri b/src/klayout.pri
index 042cf972f..f70c810ba 100644
--- a/src/klayout.pri
+++ b/src/klayout.pri
@@ -162,16 +162,25 @@ msvc {
   QMAKE_CXXFLAGS_WARN_ON += \
       -pedantic \
       -Woverloaded-virtual \
-      -Wsign-promo \
       -Wsynth \
       -Wno-deprecated \
       -Wno-long-long \
       -Wno-strict-aliasing \
       -Wno-deprecated-declarations \
-      -Wno-reserved-user-defined-literal \
 
-  # because we use unordered_map/unordered_set:
-  QMAKE_CXXFLAGS += -std=c++11
+  # too noisy on Qt:
+  # QMAKE_CXXFLAGS_WARN_ON += \
+  #     -Wsign-promo \
+  #     -Wno-reserved-user-defined-literal \
+  #
+
+  lessThan(QT_MAJOR_VERSION, 6) {
+    # because we use unordered_map/unordered_set:
+    QMAKE_CXXFLAGS += -std=c++11
+  } else {
+    # because we use unordered_map/unordered_set:
+    QMAKE_CXXFLAGS += -std=c++17
+  }
 
   win32 {
 
diff --git a/src/lym/unit_tests/lymBasicTests.cc b/src/lym/unit_tests/lymBasicTests.cc
index d0b2eaf14..90fac66bb 100644
--- a/src/lym/unit_tests/lymBasicTests.cc
+++ b/src/lym/unit_tests/lymBasicTests.cc
@@ -53,13 +53,13 @@ private:
   std::string m_text;
 };
 
+#if defined(HAVE_RUBY)
+
 static std::string np (const std::string &s)
 {
   return tl::replaced (s, "\\", "/");
 }
 
-#if defined(HAVE_RUBY)
-
 TEST(1_BasicRuby)
 {
   tl_assert (rba::RubyInterpreter::instance () != 0);