diff --git a/validator/vars.go b/validator/vars.go
index c386b6b9..f2934caf 100644
--- a/validator/vars.go
+++ b/validator/vars.go
@@ -180,7 +180,7 @@ func (v *varValidator) validateVarType(typ *ast.Type, val reflect.Value) (reflec
 		return val, gqlerror.ErrorPathf(v.path, "cannot use %s as %s", kind.String(), typ.NamedType)
 	case ast.InputObject:
 		if val.Kind() != reflect.Map {
-			return val, gqlerror.ErrorPathf(v.path, "must be a %s", def.Name)
+			return val, gqlerror.ErrorPathf(v.path, "must be a %s, not a %s", def.Name, val.Kind())
 		}
 
 		// check for unknown fields
diff --git a/validator/vars_test.go b/validator/vars_test.go
index b26a9db7..ee3c4a04 100644
--- a/validator/vars_test.go
+++ b/validator/vars_test.go
@@ -53,7 +53,7 @@ func TestValidateVars(t *testing.T) {
 			_, gerr := validator.VariableValues(schema, q.Operations.ForName(""), map[string]interface{}{
 				"var": "hello",
 			})
-			require.EqualError(t, gerr, "input: variable.var must be a InputType")
+			require.EqualError(t, gerr, "input: variable.var must be a InputType, not a string")
 		})
 
 		t.Run("defaults", func(t *testing.T) {