diff --git a/src/libslic3r/GCode/GCodeProcessor.cpp b/src/libslic3r/GCode/GCodeProcessor.cpp
index 5077069d02..c3489a621b 100644
--- a/src/libslic3r/GCode/GCodeProcessor.cpp
+++ b/src/libslic3r/GCode/GCodeProcessor.cpp
@@ -2672,6 +2672,7 @@ void GCodeProcessor::process_G1(const GCodeReader::GCodeLine& line)
             const Vec3f new_pos = m_result.moves.back().position - m_extruder_offsets[m_extruder_id];
             const std::optional<Vec3f> first_vertex = m_seams_detector.get_first_vertex();
             // the threshold value = 0.0625f == 0.25 * 0.25 is arbitrary, we may find some smarter condition later
+
             if ((new_pos - *first_vertex).squaredNorm() < 0.0625f) {
                 set_end_position(0.5f * (new_pos + *first_vertex));
                 store_move_vertex(EMoveType::Seam);
@@ -2681,6 +2682,10 @@ void GCodeProcessor::process_G1(const GCodeReader::GCodeLine& line)
             m_seams_detector.activate(false);
         }
     }
+    else if (type == EMoveType::Extrude && m_extrusion_role == erExternalPerimeter) {
+        m_seams_detector.activate(true);
+        m_seams_detector.set_first_vertex(m_result.moves.back().position - m_extruder_offsets[m_extruder_id]);
+    }
 
     // store move
     store_move_vertex(type);