diff --git a/meta/classes-recipe/setuptools3_legacy.bbclass b/meta/classes-recipe/setuptools3_legacy.bbclass
index 8197f443c9..6b51b9796b 100644
--- a/meta/classes-recipe/setuptools3_legacy.bbclass
+++ b/meta/classes-recipe/setuptools3_legacy.bbclass
@@ -30,6 +30,20 @@ SETUPTOOLS_PYTHON:class-native = "nativepython3"
 
 SETUPTOOLS_SETUP_PATH ?= "${S}"
 
+python do_check_backend() {
+    import re
+    filename = d.expand("${SETUPTOOLS_SETUP_PATH}/pyproject.toml")
+    if os.path.exists(filename):
+        for line in open(filename):
+            match = re.match(r"build-backend\s*=\s*\W([\w.]+)\W", line)
+            if not match: continue
+
+            msg = f"inherits setuptools3_legacy but has pyproject.toml with {match[1]}, use the correct class"
+            if "pep517-backend" not in (d.getVar("INSANE_SKIP") or "").split():
+                oe.qa.handle_error("pep517-backend", msg, d)
+}
+addtask check_backend after do_patch before do_configure
+
 setuptools3_legacy_do_configure() {
     :
 }