diff --git a/HB/common/database.elpi b/HB/common/database.elpi
index 425a8b52..0cd6a1ce 100644
--- a/HB/common/database.elpi
+++ b/HB/common/database.elpi
@@ -370,14 +370,16 @@ pred mixin-instance-type->mixin-src.aux
   i:term, % head of the original application
   i:mixinname, % name of mixin
   i:term, % instance body
+  i:list prop, % decl list
   i:list prop, % Cond list
   o:prop.
-mixin-instance-type->mixin-src.aux [] T M I Cond (mixin-src T M I :- Cond).
-mixin-instance-type->mixin-src.aux [A|Args] T M I Cond  (pi a \ C a) :-
+mixin-instance-type->mixin-src.aux [] T M I Decls Cond (mixin-src T M I :- std.do! DeclsCond) :-
+	std.append Decls Cond DeclsCond.
+mixin-instance-type->mixin-src.aux [A|Args] T M I Decls Cond  (pi a \ C a) :-
   pi a \
   sigma Ta\
     coq.mk-app T [a] Ta,
-    mixin-instance-type->mixin-src.aux Args Ta M I [coq.unify-eq A a ok|Cond] (C a).
+    mixin-instance-type->mixin-src.aux Args Ta M I Decls [coq.unify-eq A a ok|Cond] (C a).
 
 
 % transforms the type of a mixin instance into a
@@ -386,25 +388,27 @@ pred mixin-instance-type->mixin-src
   i:term, % type of the instance Ty
   i:mixinname, % name of mixin
   i:term, % instance body I of type Ty
+	i:list prop,
   i:list prop, % Cond list
   o:prop.
 
-mixin-instance-type->mixin-src (app _ as F) M I Cond C :-
+mixin-instance-type->mixin-src (app _ as F) M I Decls' Cond C :-
   factory? F (triple _ _ Subject),
   safe-dest-app Subject Hd Args,
-  mixin-instance-type->mixin-src.aux Args Hd M I Cond C.
+	std.rev Decls' Decls,
+  mixin-instance-type->mixin-src.aux Args Hd M I Decls Cond C.
 
-mixin-instance-type->mixin-src (prod N_ _ F) M I Cond (pi a \ C a) :-
+mixin-instance-type->mixin-src (prod N_ T F) M I Decls Cond (pi a \ C a) :-
   pi a\
   sigma  Ia \
   coq.mk-app I [a] Ia,
-    mixin-instance-type->mixin-src (F a) M Ia Cond (C a).
+    mixin-instance-type->mixin-src (F a) M Ia [coq.typecheck a T ok|Decls] Cond (C a).
 
 pred has-mixin-instance->mixin-src i:prop, o:prop.
 has-mixin-instance->mixin-src (has-mixin-instance _ M IHd) C :- std.do![
   T = global IHd,
   coq.env.typeof IHd Ty,
-  mixin-instance-type->mixin-src Ty M T [] C,
+  mixin-instance-type->mixin-src Ty M T [] [] C,
 ].
 
 pred get-canonical-structures i:term, o:list structure.
diff --git a/tests/unit/mk_src_map.v b/tests/unit/mk_src_map.v
index 2be9718a..01d03776 100644
--- a/tests/unit/mk_src_map.v
+++ b/tests/unit/mk_src_map.v
@@ -12,15 +12,17 @@ Check list_foo.
 Elpi Query HB.structure lp:{{
 
 has-mixin-instance->mixin-src (has-mixin-instance (cs-gref{{:gref list}}) {{:gref is_foo.axioms_}} {{:gref list_foo}}) MS,
+  coq.env.typeof {{:gref list_foo}} (prod _ T _),
     MS = (pi a b \ 
         mixin-src (app [{{list}}, b]) ({{:gref is_foo.axioms_}}) (app [{{list_foo}}, a]) 
-            :- [coq.unify-eq a b ok])
+            :- std.do! [coq.typecheck a T ok, coq.unify-eq a b ok])
 }}.
 
 Elpi Query HB.structure lp:{{
 
 has-mixin-instance->mixin-src (has-mixin-instance (cs-gref{{:gref list}}) {{:gref is_foo.axioms_}} {{:gref list_foo'}}) MS',
+  coq.env.typeof {{:gref list_foo'}} (prod _ T (p\ prod _ T' _)),
 MS' = (pi p a b \ 
     mixin-src (app [{{list}}, b]) {{:gref is_foo.axioms_}} (app [{{list_foo'}}, p,a])
-        :- [coq.unify-eq  a b ok]).
-}}.
\ No newline at end of file
+        :- std.do! [coq.typecheck p T ok, coq.typecheck a T' ok, coq.unify-eq a b ok]).
+}}.