diff --git a/src/typechecker/context-reduction.lisp b/src/typechecker/context-reduction.lisp
index fb4a09f2e..a24322412 100644
--- a/src/typechecker/context-reduction.lisp
+++ b/src/typechecker/context-reduction.lisp
@@ -268,11 +268,28 @@ Returns (VALUES deferred-preds retained-preds defaultable-preds)"
         :do (setf subs (compose-substitution-lists subs (fundep-entail% env expr-preds pred known-tyvars)))
         :finally (return subs)))
 
+(defun expand-pred-into-superclasses (env pred)
+  "This function finds the class in ENV associated with PRED and
+recursively appends superclass predicates, with appropriate type
+substitutions."
+  (declare (type environment env)
+           (type ty-predicate pred)
+           (values ty-predicate-list &optional))
+  (let* ((class (lookup-class env (ty-predicate-class pred)))
+         (subs (mapcan #'match
+                       (ty-predicate-types (ty-class-predicate class))
+                       (ty-predicate-types pred))))
+    (cons pred (loop :for super-pred :in (ty-class-superclasses class)
+                     :for corrected-super-pred := (apply-substitution subs super-pred)
+                     :append (expand-pred-into-superclasses env corrected-super-pred)))))
+
 (defun fundep-entail% (env expr-preds pred known-tyvars)
   (let ((class (lookup-class env (ty-predicate-class pred))))
     (unless (ty-class-fundeps class)
       (return-from fundep-entail% nil))
 
+    (setf expr-preds (mapcan (lambda (p) (expand-pred-into-superclasses env p)) expr-preds))
+
     (let* ((unknown-indices nil)
 
            (known-indices
diff --git a/tests/fundep-tests.lisp b/tests/fundep-tests.lisp
index 0ebc2fbae..86c09ef65 100644
--- a/tests/fundep-tests.lisp
+++ b/tests/fundep-tests.lisp
@@ -147,3 +147,19 @@
       (let ((filled?
               (fn (i) (coalton-library/optional:some? (moo-find moo i)))))
         (coalton-library/iterator:filter! filled? (coalton-library/iterator:up-to (moo-size moo)))))"))
+
+(deftest fundep-superclass-resolution ()
+  ;; See https://github.com/coalton-lang/coalton/issues/1050
+  (check-coalton-types
+   "(define-class (RandomAccessBase :f :t (:f -> :t))
+      (make (UFix -> :t -> :f))
+      (rab-length (:f -> UFix)))
+
+    (define-class (RandomAccessBase :f :t => RandomAccessReadable :f :t (:f -> :t))
+      (unsafe-set! (:f -> UFix -> :t)))
+
+    (declare aref (RandomAccessReadable :f :t => :f -> UFix -> (Optional :t)))
+    (define (aref storage index)
+      (if (and (<= 0 index) (< index (rab-length storage)))
+          (Some (unsafe-set! storage index))
+          None)))"))