diff --git a/test/aeso_compiler_tests.erl b/test/aeso_compiler_tests.erl
index 192da86..7e8f2f0 100644
--- a/test/aeso_compiler_tests.erl
+++ b/test/aeso_compiler_tests.erl
@@ -836,6 +836,16 @@ failing_contracts() ->
                   [<<?Pos(7,10)
                      "Unimplemented function f from the interface I in the contract C">>
                   ])
+    , ?TYPE_ERROR(contract_interface_polymorphism_same_name_same_type,
+                  [<<?Pos(7,10)
+                     "Unimplemented function f from the interface I1 in the contract C">>
+                  ])
+    , ?TYPE_ERROR(contract_interface_polymorphism_same_name_different_type,
+                  [<<?Pos(9,5)
+                     "Duplicate definitions of f at\n"
+                     "  - line 8, column 5\n"
+                     "  - line 9, column 5">>
+                  ])
     , ?TYPE_ERROR(contract_polymorphism_missing_implementation,
                   [<<?Pos(7,10)
                      "Unimplemented function f from the interface I1 in the contract C">>
diff --git a/test/contracts/contract_interface_polymorphism_same_name_different_type.aes b/test/contracts/contract_interface_polymorphism_same_name_different_type.aes
new file mode 100644
index 0000000..d324c11
--- /dev/null
+++ b/test/contracts/contract_interface_polymorphism_same_name_different_type.aes
@@ -0,0 +1,9 @@
+contract interface I1 =
+    entrypoint f : () => int
+
+contract interface I2 : I1 =
+    entrypoint f : () => char
+
+contract C : I2 =
+    entrypoint f() = 1
+    entrypoint f() = 'c'
diff --git a/test/contracts/contract_interface_polymorphism_same_name_same_type.aes b/test/contracts/contract_interface_polymorphism_same_name_same_type.aes
new file mode 100644
index 0000000..20ab99f
--- /dev/null
+++ b/test/contracts/contract_interface_polymorphism_same_name_same_type.aes
@@ -0,0 +1,8 @@
+contract interface I1 =
+    entrypoint f : () => int
+
+contract interface I2 : I1 =
+    entrypoint f : () => int
+
+contract C : I2 =
+    entrypoint f() = 1