diff --git a/src/protocol/tests/parser_binding.rs b/src/protocol/tests/parser_binding.rs
index 4aa276e9371a3b41772ecf8e7feb2b99b8c4b935..b097f3e748a6d077357c992b4bcb58d93461783a 100644
--- a/src/protocol/tests/parser_binding.rs
+++ b/src/protocol/tests/parser_binding.rs
@@ -60,6 +60,48 @@ fn test_incorrect_binding() {
     });
 }
 
+#[test]
+fn test_incorrect_binding_variable() {
+    // Note: if variable already exists then it is interpreted at the binding
+    // expression as value. So the case where "the variable is already defined"
+    // results in no binding variable.
+
+    Tester::new_single_source_expect_err("binding var in next scope", "
+        union Option<T>{ Some(T), None }
+        func foo() -> bool {
+            auto opt = Option::Some(false);
+            if (let Option::Some(var) = opt) {
+                auto var = true; // should mismatch against binding 'var'
+                return var;
+            }
+            return false;
+        }
+    ").error(|e| { e
+        .assert_num(2)
+        .assert_msg_has(0, "variable name conflicts")
+        .assert_occurs_at(0, "var = true;")
+        .assert_occurs_at(1, "var) = opt");
+    });
+
+    Tester::new_single_source_expect_err("binding var in nested scope", "
+        union LR<A, B>{ L(A), R(B) }
+        func foo() -> u32 {
+            LR<auto, u32> x = LR::L(5);
+            if (let LR::L(y) = x) {
+                if (true) {
+                    auto y = 5;
+                    return y;
+                }
+            }
+        }
+    ").error(|e| { e
+        .assert_num(2)
+        .assert_msg_has(0, "variable name conflicts")
+        .assert_occurs_at(0, "y = 5")
+        .assert_occurs_at(1, "y) = x");
+    });
+}
+
 #[test]
 fn test_boolean_ops_on_binding() {
     Tester::new_single_source_expect_ok("apply && to binding result", "