diff --git a/constraint.cpp b/constraint.cpp
index 63ef565..9556a9e 100644
--- a/constraint.cpp
+++ b/constraint.cpp
@@ -496,7 +496,7 @@ void Constraint::Generate(IdList<Equation,hEquation> *l) {
         case PT_ON_CIRCLE: {
             Entity *circle = SS.GetEntity(entityA);
             hEntity center = circle->point[0];
-            Expr *radius = SS.GetEntity(circle->distance)->DistanceGetExpr();
+            Expr *radius = circle->CircleGetRadiusExpr();
             AddEq(l, Distance(workplane, ptA, center)->Minus(radius), 0);
             break;
         }
diff --git a/entity.cpp b/entity.cpp
index 9e802f0..b713dbb 100644
--- a/entity.cpp
+++ b/entity.cpp
@@ -73,7 +73,7 @@ Vector Entity::VectorGetRefPoint(void) {
 }
 
 bool Entity::IsCircle(void) {
-    return (type == CIRCLE);
+    return (type == CIRCLE) || (type == ARC_OF_CIRCLE);
 }
 
 Expr *Entity::CircleGetRadiusExpr(void) {
diff --git a/polygon.h b/polygon.h
index 47eb245..0369f84 100644
--- a/polygon.h
+++ b/polygon.h
@@ -43,8 +43,8 @@ class SEdgeList {
 public:
     SList<SEdge>    l;
 
-    void InsertEdgeBreaking(SEdge *e);
     bool AssemblePolygon(SPolygon *dest, SEdge *errorAt);
+    void BreakEdgesInto(SEdgeList *el);
 };
 
 class SPoint {
diff --git a/sketch.cpp b/sketch.cpp
index b3aaf7a..d430c21 100644
--- a/sketch.cpp
+++ b/sketch.cpp
@@ -74,6 +74,7 @@ void Group::MenuGroup(int id) {
         case GraphicsWindow::MNU_GROUP_EXTRUDE:
             g.type = EXTRUDE;
             g.opA = SS.GW.activeGroup;
+            g.wrkpl.entityB = SS.GW.activeWorkplane;
             g.name.strcpy("extrude");
             break;
 
@@ -207,6 +208,7 @@ void Group::Generate(IdList<Entity,hEntity> *entity,
 }
 
 void Group::GenerateEquations(IdList<Equation,hEquation> *l) {
+    Equation eq;
     if(type == ROTATE) {
         // Normalize the quaternion
         ExprQuaternion q = {
@@ -214,10 +216,25 @@ void Group::GenerateEquations(IdList<Equation,hEquation> *l) {
             Expr::FromParam(h.param(4)),
             Expr::FromParam(h.param(5)),
             Expr::FromParam(h.param(6)) };
-        Equation eq;
         eq.e = (q.Magnitude())->Minus(Expr::FromConstant(1));
         eq.h = h.equation(0);
         l->Add(&eq);
+    } else if(type == EXTRUDE) {
+        if(wrkpl.entityB.v != Entity::FREE_IN_3D.v) {
+            Entity *w = SS.GetEntity(wrkpl.entityB);
+            ExprVector u = w->Normal()->NormalExprsU();
+            ExprVector v = w->Normal()->NormalExprsV();
+            ExprVector extruden = {
+                Expr::FromParam(h.param(0)),
+                Expr::FromParam(h.param(1)),
+                Expr::FromParam(h.param(2)) };
+            eq.e = u.Dot(extruden);
+            eq.h = h.equation(0);
+            l->Add(&eq);
+            eq.e = v.Dot(extruden);
+            eq.h = h.equation(1);
+            l->Add(&eq);
+        }
     }
 }
 
diff --git a/sketch.h b/sketch.h
index 7ae0f48..92b08d2 100644
--- a/sketch.h
+++ b/sketch.h
@@ -419,7 +419,7 @@ inline hEntity hGroup::entity(int i)
 inline hParam hGroup::param(int i)
     { hParam r; r.v = 0x80000000 | (v << 16) | i; return r; }
 inline hEquation hGroup::equation(int i)
-    { if(i != 0) oops(); hEquation r; r.v = v | 0x80000000; return r; }
+    { hEquation r; r.v = (v << 16) | 0x80000000 | i; return r; }
 
 inline bool hRequest::IsFromReferences(void) {
     if(v == Request::HREQUEST_REFERENCE_XY.v) return true;