diff --git a/Lib/abc.py b/Lib/abc.py
index f9b49ac3d1c..0f980363046 100644
--- a/Lib/abc.py
+++ b/Lib/abc.py
@@ -94,7 +94,7 @@ def __new__(mcls, name, bases, namespace):
 
     def register(cls, subclass):
         """Register a virtual subclass of an ABC."""
-        if not isinstance(cls, type):
+        if not isinstance(subclass, type):
             raise TypeError("Can only register classes")
         if issubclass(subclass, cls):
             return  # Already a subclass
diff --git a/Lib/test/test_abc.py b/Lib/test/test_abc.py
index c3482d6f63d..51fd9bbfb0f 100644
--- a/Lib/test/test_abc.py
+++ b/Lib/test/test_abc.py
@@ -139,6 +139,12 @@ class C(A):
         self.assertRaises(RuntimeError, C.register, A)  # cycles not allowed
         C.register(B)  # ok
 
+    def test_register_non_class(self):
+        class A(metaclass=abc.ABCMeta):
+            pass
+        self.assertRaisesRegexp(TypeError, "Can only register classes",
+                                A.register, 4)
+
     def test_registration_transitiveness(self):
         class A(metaclass=abc.ABCMeta):
             pass
diff --git a/Misc/NEWS b/Misc/NEWS
index 2a66d01d199..e3d94da82db 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -73,6 +73,8 @@ Core and Builtins
 Library
 -------
 
+- Issue #7792: Registering non-classes to ABCs raised an obscure error.
+
 - Issue #7785: Don't accept bytes in FileIO.write().
 
 - Issue #7773: Fix an UnboundLocalError in platform.linux_distribution() when