diff --git a/src/libslic3r/CadDocument.cpp b/src/libslic3r/CadDocument.cpp
index caf46280ce..de50cc1da1 100644
--- a/src/libslic3r/CadDocument.cpp
+++ b/src/libslic3r/CadDocument.cpp
@@ -1930,7 +1930,18 @@ TopoDS_Wire CadDocument::build_sketch_wire(const CadFeature& sketch) const
     if (!sketch.entities.empty()) {
         TopoDS_Wire w = SketchEngine::entities_to_wire(sketch.entities, sketch.plane);
         if (!w.IsNull()) return w;
-        // fall through to legacy paths if entities produced nothing
+        // An entity sketch that yields no wire is an ERROR, not a cue to fall through. The
+        // legacy tail of this function ends in a default rectangle built from width/height,
+        // which for an entity sketch are whatever they happened to be initialised to — so a
+        // sketch entities_to_wire cannot handle (a circle coexisting with a line, two circles:
+        // snaporca-88v) used to extrude into a box the user never drew, silently. Failing here
+        // costs the caller an error message; falling through cost them wrong geometry that
+        // looked deliberate. The legacy profile/shape paths below are still reached by sketches
+        // that legitimately carry no entities at all.
+        throw std::runtime_error(
+            "sketch has entities but they do not form a single closed wire — a closed entity "
+            "(circle/ellipse) combined with other entities, or several closed entities, is not "
+            "supported yet");
     }
     if (!sketch.profile.points.empty()) {
         SketchProfile prof = sketch.profile;
diff --git a/tests/libslic3r/test_caddocument.cpp b/tests/libslic3r/test_caddocument.cpp
index e90f3d2013..e35204566a 100644
--- a/tests/libslic3r/test_caddocument.cpp
+++ b/tests/libslic3r/test_caddocument.cpp
@@ -6726,7 +6726,8 @@ TEST_CASE("A cut that removes no material is an error, not a silent success", "[
         // And the body is left as it was, not half-applied.
         CadDocument again = box();
         REQUIRE(again.recompute());
-        CHECK(again.body_mass_properties(0).volume == Approx(solid).margin(1e-6));
+        CHECK_THAT(again.body_mass_properties(0).volume,
+                   Catch::Matchers::WithinAbs(solid, 1e-6));
     }
 
     SECTION("the same hole on the body still works") {
@@ -6735,8 +6736,8 @@ TEST_CASE("A cut that removes no material is an error, not a silent success", "[
         const double solid = doc.body_mass_properties(0).volume;
         doc.add_hole(8.0, 20.0, true, 0.0, 0.0, SketchPlane::XY(), "Hole");
         REQUIRE(doc.recompute());
-        CHECK(doc.body_mass_properties(0).volume
-              == Approx(solid - M_PI * 16.0 * 20.0).epsilon(0.01));
+        CHECK_THAT(doc.body_mass_properties(0).volume,
+                   Catch::Matchers::WithinRel(solid - M_PI * 16.0 * 20.0, 0.01));
     }
 
     SECTION("a cut-mode extrude that misses is rejected too") {
@@ -6752,3 +6753,48 @@ TEST_CASE("A cut that removes no material is an error, not a silent success", "[
         CHECK(doc.error.find("removed no material") != std::string::npos);
     }
 }
+
+// entities_to_wire handles exactly two shapes: one lone closed entity, or a chain of open ones.
+// Anything else returns a null wire, and build_sketch_wire used to answer that by falling through
+// to its legacy tail — which ends in a rectangle built from width/height. For an entity sketch
+// those are whatever they were initialised to, so the extrude produced a box nobody drew.
+// snaporca-88v.
+TEST_CASE("An entity sketch that forms no wire fails instead of extruding a default box", "[CadDocument]")
+{
+    auto circle = [](Vec2d c, double r) {
+        SketchEntity e; e.type = SketchEntity::Type::Circle; e.center = c; e.p0 = c; e.radius = r;
+        return e;
+    };
+    auto line = [](Vec2d a, Vec2d b) {
+        SketchEntity e; e.type = SketchEntity::Type::Line; e.p0 = a; e.p1 = b;
+        return e;
+    };
+
+    SECTION("a lone circle still works — the supported case is untouched") {
+        CadDocument doc;
+        int sk = doc.add_sketch_entities({ circle({0, 0}, 10.0) }, SketchPlane::XY(), "Sketch");
+        doc.add_extrude(sk, 5.0, false, BooleanMode::New, "Extrude");
+        REQUIRE(doc.recompute());
+        CHECK_THAT(doc.body_mass_properties(0).volume,
+                   Catch::Matchers::WithinRel(M_PI * 100.0 * 5.0, 0.01));
+    }
+
+    SECTION("circle + stray line is rejected, not silently turned into a box") {
+        CadDocument doc;
+        int sk = doc.add_sketch_entities({ circle({0, 0}, 10.0), line({40, 40}, {60, 40}) },
+                                        SketchPlane::XY(), "Sketch");
+        doc.add_extrude(sk, 5.0, false, BooleanMode::New, "Extrude");
+        CHECK_FALSE(doc.recompute());
+        CHECK(doc.error.find("do not form a single closed wire") != std::string::npos);
+        CHECK(doc.bodies.empty());
+    }
+
+    SECTION("two circles are rejected too") {
+        CadDocument doc;
+        int sk = doc.add_sketch_entities({ circle({-20, 0}, 8.0), circle({20, 0}, 8.0) },
+                                        SketchPlane::XY(), "Sketch");
+        doc.add_extrude(sk, 5.0, false, BooleanMode::New, "Extrude");
+        CHECK_FALSE(doc.recompute());
+        CHECK(doc.error.find("do not form a single closed wire") != std::string::npos);
+    }
+}