diff --git a/testlabl/poly.exp b/testlabl/poly.exp
index c51b9cdff..f3e36070c 100644
--- a/testlabl/poly.exp
+++ b/testlabl/poly.exp
@@ -249,4 +249,6 @@ Type 'a u t should be an instance of g t
 type 'a v = 'a u t constraint 'a = int
 #     Characters 38-58:
 In the definition of v, type 'a list u should be 'a u
+#       type 'a t = 'a
+type 'a u = A of 'a t
 # 
diff --git a/testlabl/poly.exp2 b/testlabl/poly.exp2
index dbb61ab41..416dce1e8 100644
--- a/testlabl/poly.exp2
+++ b/testlabl/poly.exp2
@@ -256,4 +256,6 @@ Type 'a u t should be an instance of g t
 type 'a v = 'a u t constraint 'a = int
 #     Characters 38-58:
 In the definition of v, type 'a list u should be 'a u
+#       type 'a t = 'a
+type 'a u = A of 'a t
 # 
diff --git a/testlabl/poly.ml b/testlabl/poly.ml
index 7f7986ee2..f58f61377 100644
--- a/testlabl/poly.ml
+++ b/testlabl/poly.ml
@@ -409,3 +409,7 @@ type 'a u = 'a and 'a v = 'a u t constraint 'a = int;;
 
 (* Example of wrong expansion *)
 type 'a u = < m : 'a v > and 'a v = 'a list u;;
+
+(* PR#1744: Ctype.matches *)
+type 'a t = 'a
+type 'a u = A of 'a t;;
diff --git a/typing/ctype.ml b/typing/ctype.ml
index a2b1b2b09..7a9066deb 100644
--- a/typing/ctype.ml
+++ b/typing/ctype.ml
@@ -2092,11 +2092,11 @@ let rigidify ty =
   unmark_type ty;
   !vars
 
-let all_distinct_vars vars =
+let all_distinct_vars env vars =
   let tyl = ref [] in
   List.for_all
     (fun ty ->
-      let ty = repr ty in
+      let ty = expand_head env ty in
       if List.memq ty !tyl then false else
       (tyl := ty :: !tyl; ty.desc = Tvar))
     vars
@@ -2105,7 +2105,7 @@ let matches env ty ty' =
   let snap = snapshot () in
   let vars = rigidify ty in
   let ok =
-    try unify env ty ty'; all_distinct_vars vars
+    try unify env ty ty'; all_distinct_vars env vars
     with Unify _ -> false
   in
   backtrack snap;
diff --git a/typing/ctype.mli b/typing/ctype.mli
index 766476d44..ae4f15dd9 100644
--- a/typing/ctype.mli
+++ b/typing/ctype.mli
@@ -153,7 +153,7 @@ val moregeneral: Env.t -> bool -> type_expr -> type_expr -> bool
 
 val rigidify: type_expr -> type_expr list
         (* "Rigidify" a type and return its type variable *)
-val all_distinct_vars: type_expr list -> bool
+val all_distinct_vars: Env.t -> type_expr list -> bool
         (* Check those types are all distinct type variables *)
 val matches : Env.t -> type_expr -> type_expr -> bool
         (* Same as [moregeneral false], implemented using the two above