diff --git a/src/common/common.hpp b/src/common/common.hpp
index 99a226630..9466d45e6 100644
--- a/src/common/common.hpp
+++ b/src/common/common.hpp
@@ -5,6 +5,7 @@
 #include <type_traits>
 #include <math.h>
 #include <array>
+#include <sstream>
 #include "lut.hpp"
 
 namespace horizon {
@@ -268,6 +269,13 @@ template <typename T> class Coord {
     {
         return {x, y};
     }
+
+    std::string str() const
+    {
+        std::stringstream ss;
+        ss << "(" << x << ", " << y << ")";
+        return ss.str();
+    }
 };
 
 
@@ -333,4 +341,47 @@ constexpr shallow_copy_t shallow_copy = shallow_copy_t();
 
 enum class CopyMode { DEEP, SHALLOW };
 
+
+template <typename T> class Segment {
+public:
+    Coord<T> from;
+    Coord<T> to;
+
+    Segment(Coord<T> a, Coord<T> b) : from(a), to(b)
+    {
+    }
+
+    bool intersect(const Segment<T> &other, Coord<T> &output) const
+    {
+        const T &x1 = from.x;
+        const T &y1 = from.y;
+        const T &x2 = to.x;
+        const T &y2 = to.y;
+        const T &x3 = other.from.x;
+        const T &y3 = other.from.y;
+        const T &x4 = other.to.x;
+        const T &y4 = other.to.y;
+
+        // See https://en.wikipedia.org/wiki/Line-line_intersection
+        double d = (x1 - x2) * (y3 - y4) - (y1 - y2) * (x3 - x4);
+        if (fabs(d) < 1e-6) {
+            return false; // Parallel or coincident
+        }
+        T a = (x1 * y2 - y1 * x2);
+        T b = (x3 * y4 - y3 * x4);
+        double x = (a * (x3 - x4) - (x1 - x2) * b) / d;
+        double y = (a * (y3 - y4) - (y1 - y2) * b) / d;
+        output.x = x;
+        output.y = y;
+        return true;
+    }
+
+    std::string str() const
+    {
+        std::stringstream ss;
+        ss << "Segment(from=" << from.str() << ", to=" << to.str() << ")";
+        return ss.str();
+    }
+};
+
 } // namespace horizon
diff --git a/src/core/tools/tool_round_off_vertex.cpp b/src/core/tools/tool_round_off_vertex.cpp
index e8ca544d6..ff69f5467 100644
--- a/src/core/tools/tool_round_off_vertex.cpp
+++ b/src/core/tools/tool_round_off_vertex.cpp
@@ -11,7 +11,8 @@ namespace horizon {
 
 bool ToolRoundOffVertex::can_begin()
 {
-    return sel_count_type(selection, ObjectType::POLYGON_VERTEX) == 1;
+    return (sel_count_type(selection, ObjectType::POLYGON_VERTEX) == 1
+            || sel_count_type(selection, ObjectType::POLYGON_ARC_CENTER) == 1);
 }
 
 int ToolRoundOffVertex::wrap_index(int i) const
@@ -27,8 +28,10 @@ int ToolRoundOffVertex::wrap_index(int i) const
 ToolResponse ToolRoundOffVertex::begin(const ToolArgs &args)
 {
     int vertex_idx = 0;
+    editing = sel_has_type(selection, ObjectType::POLYGON_ARC_CENTER);
     {
-        auto x = sel_find_one(selection, ObjectType::POLYGON_VERTEX);
+        ObjectType type = editing ? ObjectType::POLYGON_ARC_CENTER : ObjectType::POLYGON_VERTEX;
+        auto x = sel_find_one(selection, type);
         poly = doc.r->get_polygon(x.uuid);
         vertex_idx = x.vertex;
     }
@@ -36,21 +39,38 @@ ToolResponse ToolRoundOffVertex::begin(const ToolArgs &args)
     auto v_next = wrap_index(vertex_idx + 1);
     auto v_prev = wrap_index(vertex_idx - 1);
 
-    if ((poly->vertices.at(vertex_idx).type == Polygon::Vertex::Type::ARC)
-        || (poly->vertices.at(v_prev).type == Polygon::Vertex::Type::ARC)) {
-        imp->tool_bar_flash("can't round off arc");
-        return ToolResponse::end();
+
+    if (editing) {
+        auto v_inserted = v_next; // Inserted vertex
+        v_next = wrap_index(vertex_idx + 2);
+
+        vxp = &poly->vertices.at(vertex_idx);
+        vxn = &poly->vertices.at(v_inserted);
+
+        if (!revert_arc(p0, vxp->position, vxn->position, vxp->arc_center)) {
+            imp->tool_bar_flash("can't undo arc");
+            return ToolResponse::end();
+        }
+    }
+    else {
+        if ((poly->vertices.at(vertex_idx).type == Polygon::Vertex::Type::ARC)
+            || (poly->vertices.at(v_prev).type == Polygon::Vertex::Type::ARC)) {
+            imp->tool_bar_flash("can't round off arc");
+            return ToolResponse::end();
+        }
+        p0 = poly->vertices.at(vertex_idx).position;
     }
 
     selection.clear();
 
-    p0 = poly->vertices.at(vertex_idx).position;
-    vn = (Coordd(poly->vertices.at(v_next).position) - p0).normalize();
-    vp = (Coordd(poly->vertices.at(v_prev).position) - p0).normalize();
+    Coordd p1 = poly->vertices.at(v_next).position;
+    Coordd p2 = poly->vertices.at(v_prev).position;
+
+    vn = (p1 - p0).normalize();
+    vp = (p2 - p0).normalize();
     vh = (vn + vp).normalize();
 
-    delta_max = std::min((poly->vertices.at(v_next).position - poly->vertices.at(vertex_idx).position).magd(),
-                         (poly->vertices.at(v_prev).position - poly->vertices.at(vertex_idx).position).magd());
+    delta_max = std::min((p1 - p0).mag(), (p2 - p0).mag());
     alpha = acos(vh.dot(vp));
     if (isnan(alpha) || (alpha > .99 * (M_PI / 2))) {
         imp->tool_bar_flash("can't round off collinear edges");
@@ -58,18 +78,20 @@ ToolResponse ToolRoundOffVertex::begin(const ToolArgs &args)
     }
     r_max = tan(alpha) * delta_max;
 
-    const bool rev = vn.cross(vp) < 0;
+    if (!editing) {
+        const bool rev = vn.cross(vp) < 0;
 
-    if (v_next == 0) {
-        poly->vertices.emplace_back(Coordi());
-        vxn = &poly->vertices.back();
-    }
-    else {
-        vxn = &*poly->vertices.emplace(poly->vertices.begin() + v_next, Coordi());
+        if (v_next == 0) {
+            poly->vertices.emplace_back(Coordi());
+            vxn = &poly->vertices.back();
+        }
+        else {
+            vxn = &*poly->vertices.emplace(poly->vertices.begin() + v_next, Coordi());
+        }
+        vxp = &poly->vertices.at(vertex_idx);
+        vxp->type = Polygon::Vertex::Type::ARC;
+        vxp->arc_reverse = rev;
     }
-    vxp = &poly->vertices.at(vertex_idx);
-    vxp->type = Polygon::Vertex::Type::ARC;
-    vxp->arc_reverse = rev;
 
     imp->set_snap_filter({{ObjectType::POLYGON, poly->uuid}});
 
@@ -122,7 +144,7 @@ ToolResponse ToolRoundOffVertex::update(const ToolArgs &args)
     else if (args.type == ToolEventType::ACTION) {
         switch (args.action) {
         case InToolActionID::LMB:
-            if (plane_finish())
+            if (commit())
                 return ToolResponse::commit();
             else
                 return ToolResponse::revert();
@@ -153,7 +175,7 @@ ToolResponse ToolRoundOffVertex::update(const ToolArgs &args)
             }
             else if (data->event == ToolDataWindow::Event::OK) {
                 imp->dialogs.close_nonmodal();
-                if (plane_finish())
+                if (commit())
                     return ToolResponse::commit();
                 else
                     return ToolResponse::revert();
@@ -162,4 +184,27 @@ ToolResponse ToolRoundOffVertex::update(const ToolArgs &args)
     }
     return ToolResponse();
 }
+
+bool ToolRoundOffVertex::commit()
+{
+    if (radius_current < 1) {
+        // Tiny radius, just ignore it
+        if (!editing)
+            return false; // Not a modification so just revert the action
+
+        // Undo change to original vertex
+        vxp->arc_center = Coordi();
+        vxp->arc_reverse = false;
+        vxp->position = p0.to_coordi();
+        vxp->type = Polygon::Vertex::Type::LINE;
+
+        // Remove inserted vertex
+        vxn->remove = true;
+        poly->vertices.erase(
+                std::remove_if(poly->vertices.begin(), poly->vertices.end(), [](const auto &x) { return x.remove; }),
+                poly->vertices.end());
+    }
+    return plane_finish();
+}
+
 } // namespace horizon
diff --git a/src/core/tools/tool_round_off_vertex.hpp b/src/core/tools/tool_round_off_vertex.hpp
index 9c09d8d6e..95d139712 100644
--- a/src/core/tools/tool_round_off_vertex.hpp
+++ b/src/core/tools/tool_round_off_vertex.hpp
@@ -37,9 +37,11 @@ class ToolRoundOffVertex : public virtual ToolBase, public ToolHelperPlane {
     double r_max = 0;
     double alpha = 0;
     double radius_current = 0;
+    bool editing = false;
 
     void update_poly(double r);
     void update_cursor(const Coordi &c);
     void update_tip();
+    bool commit();
 };
 } // namespace horizon
diff --git a/src/util/geom_util.cpp b/src/util/geom_util.cpp
index fdaa0c702..9810205b9 100644
--- a/src/util/geom_util.cpp
+++ b/src/util/geom_util.cpp
@@ -181,4 +181,24 @@ Placement transform_text_placement_to_new_reference(Placement pl, Placement old_
     return out;
 }
 
+
+/**
+ * Determine original point that the arc rounded off. If the parameters are
+ * invalid or it cannot determine the proper value return false.
+ */
+bool revert_arc(Coordd &output, const Coordd &p0, const Coordd &p1, const Coordd &c)
+{
+    // The original center position is found by computing the intersection of
+    // lines defined by each arc point and their tangents. Tangents are of an
+    // arc perpendicular to vector to center.
+    const Coordd v0 = (p0 - c);
+    const Coordd v1 = (p1 - c);
+    double a = v0.cross(v1) > 0 ? M_PI / 2 : -M_PI / 2; // CW / CCW
+    const Coordd t0 = v0.rotate(a);
+    const Coordd t1 = v1.rotate(-a);
+    Segment<double> l0 = Segment<double>(p0, t0 + p0);
+    Segment<double> l1 = Segment<double>(p1, t1 + p1);
+    return l0.intersect(l1, output);
+}
+
 } // namespace horizon
diff --git a/src/util/geom_util.hpp b/src/util/geom_util.hpp
index 91238dde2..fbfaf1893 100644
--- a/src/util/geom_util.hpp
+++ b/src/util/geom_util.hpp
@@ -35,4 +35,6 @@ template <typename T> T c2pi(T x);
 Placement transform_package_placement_to_new_reference(Placement pl, Placement old_ref, Placement new_ref);
 Placement transform_text_placement_to_new_reference(Placement pl, Placement old_ref, Placement new_ref);
 
+bool revert_arc(Coordd &output, const Coordd &p0, const Coordd &p1, const Coordd &c);
+
 } // namespace horizon