diff --git a/src/mesh.cpp b/src/mesh.cpp
index 7767901..52f8c0b 100644
--- a/src/mesh.cpp
+++ b/src/mesh.cpp
@@ -186,7 +186,7 @@ void SMesh::Simplify(int start) {
                     if(fabs(bDot) < LENGTH_EPS && fabs(dDot) < LENGTH_EPS) {
                         conv[WRAP((j+1), convc)] = c;
                         // and remove the vertex at j, which is a dup
-                        std::move(conv+j+1, conv+convc, conv+(convc-1));
+                        std::move(conv+j+1, conv+convc, conv+j);
                         convc--;
                     } else if(fabs(bDot) < LENGTH_EPS && dDot > 0) {
                         conv[j] = c;
@@ -194,7 +194,7 @@ void SMesh::Simplify(int start) {
                         conv[WRAP((j+1), convc)] = c;
                     } else if(bDot > 0 && dDot > 0) {
                         // conv[j] is unchanged, conv[j+1] goes to [j+2]
-                        std::move_backward(conv+j+1, conv+convc, conv+j+2);
+                        std::move_backward(conv+j+1, conv+convc, conv+convc+1);
                         conv[j+1] = c;
                         convc++;
                     } else {