diff --git a/src/libslic3r/GCode/WipeTower.cpp b/src/libslic3r/GCode/WipeTower.cpp
index 3d7353eadf..cfa407ea73 100644
--- a/src/libslic3r/GCode/WipeTower.cpp
+++ b/src/libslic3r/GCode/WipeTower.cpp
@@ -617,6 +617,11 @@ Polygon generate_rectange_polygon(const Vec2f &wt_box_min ,const Vec2f & wt_box_
     return res;
 }
 
+const char* flush_planner_queue_command(GCodeFlavor flavor)
+{
+    return flavor == gcfKlipper ? "M400\n" : "G4 S0\n";
+}
+
 class WipeTowerWriter
 {
 public:
@@ -1190,7 +1195,7 @@ public:
 
 	WipeTowerWriter& flush_planner_queue()
 	{
-		m_gcode += "G4 S0\n";
+		m_gcode += flush_planner_queue_command(m_gcode_flavor);
 		return *this;
 	}
 
diff --git a/src/libslic3r/GCode/WipeTower.hpp b/src/libslic3r/GCode/WipeTower.hpp
index 66e8acf1c4..a083da1fb2 100644
--- a/src/libslic3r/GCode/WipeTower.hpp
+++ b/src/libslic3r/GCode/WipeTower.hpp
@@ -26,6 +26,14 @@ enum GCodeFlavor : unsigned char;
 Polylines construct_gap_for_skip_points(
     const Polygon& polygon, const std::vector<Vec2f>& skip_points, float wt_width, float gap_length, Polygon& insert_skip_polygon);
 
+// Returns the command that makes the firmware finish its queued moves, so a command or
+// custom-G-code boundary right after (resetting the extruder position, entering
+// [change_filament_gcode] / [filament_start_gcode]) is not reached early. Klipper acts on
+// such commands the moment it parses them, and its G4 reads only P, so the zero dwell the
+// other flavors use synchronizes nothing there — M400 does. Defined in WipeTower.cpp, shared
+// by WipeTower and WipeTower2.
+const char* flush_planner_queue_command(GCodeFlavor flavor);
+
 class WipeTower
 {
 public:
diff --git a/src/libslic3r/GCode/WipeTower2.cpp b/src/libslic3r/GCode/WipeTower2.cpp
index 51ab155dd9..5dc78d4785 100644
--- a/src/libslic3r/GCode/WipeTower2.cpp
+++ b/src/libslic3r/GCode/WipeTower2.cpp
@@ -386,7 +386,8 @@ public:
     }
 
     WipeTowerWriter2& switch_filament_monitoring(bool enable) {
-        m_gcode += std::string("G4 S0\n") + "M591 " + (enable ? "R" : "S0") + "\n";
+        m_gcode += flush_planner_queue_command(m_gcode_flavor);
+        m_gcode += std::string("M591 ") + (enable ? "R" : "S0") + "\n";
         return *this;
     }
 
@@ -625,7 +626,7 @@ public:
 	// Set extruder temperature, don't wait by default.
 	WipeTowerWriter2& set_extruder_temp(int temperature, bool wait = false)
 	{
-        m_gcode += "G4 S0\n"; // to flush planner queue
+        m_gcode += flush_planner_queue_command(m_gcode_flavor);
         m_gcode += "M" + std::to_string(wait ? 109 : 104) + " S" + std::to_string(temperature) + "\n";
         return *this;
     }
@@ -677,8 +678,8 @@ public:
     }
 
 	WipeTowerWriter2& flush_planner_queue()
-	{ 
-		m_gcode += "G4 S0\n"; 
+	{
+		m_gcode += flush_planner_queue_command(m_gcode_flavor);
 		return *this;
 	}
 
diff --git a/tests/fff_print/CMakeLists.txt b/tests/fff_print/CMakeLists.txt
index 70ab639faa..08f86de8a7 100644
--- a/tests/fff_print/CMakeLists.txt
+++ b/tests/fff_print/CMakeLists.txt
@@ -18,6 +18,7 @@ add_executable(${_TEST_NAME}_tests
 	test_slicing_pipeline_hook.cpp
 	test_support_material.cpp
 	test_trianglemesh.cpp
+	test_wipe_tower.cpp
 	)
 target_link_libraries(${_TEST_NAME}_tests test_common libslic3r Catch2::Catch2WithMain)
 set_property(TARGET ${_TEST_NAME}_tests PROPERTY FOLDER "tests")
diff --git a/tests/fff_print/test_wipe_tower.cpp b/tests/fff_print/test_wipe_tower.cpp
new file mode 100644
index 0000000000..de5836ba7a
--- /dev/null
+++ b/tests/fff_print/test_wipe_tower.cpp
@@ -0,0 +1,27 @@
+#include <catch2/catch_all.hpp>
+
+#include <string>
+
+#include "libslic3r/GCode/WipeTower.hpp"
+#include "libslic3r/PrintConfig.hpp"
+
+using namespace Slic3r;
+
+// The wipe tower flushes the firmware's motion queue before a command or custom-G-code
+// boundary that must not be reached early (an extruder-position reset, entering custom
+// G-code). Klipper acts on those the moment it parses them, and its G4 reads only P, so the
+// zero dwell every other flavor uses is not a flush there.
+TEST_CASE("Klipper flushes the wipe tower planner queue with M400", "[WipeTower]")
+{
+    CHECK(std::string(flush_planner_queue_command(gcfKlipper)) == "M400\n");
+}
+
+TEST_CASE("Other flavors flush the wipe tower planner queue with a zero dwell", "[WipeTower]")
+{
+    const GCodeFlavor flavor = GENERATE(gcfMarlinLegacy, gcfRepRapFirmware, gcfRepetier,
+                                        gcfMarlinFirmware, gcfRepRapSprinter, gcfTeacup,
+                                        gcfMakerWare, gcfSailfish, gcfMach3, gcfMachinekit,
+                                        gcfSmoothie, gcfNoExtrusion);
+    INFO("gcode flavor enum value: " << int(flavor));
+    CHECK(std::string(flush_planner_queue_command(flavor)) == "G4 S0\n");
+}