diff --git a/binding/form_mapping.go b/binding/form_mapping.go
index e76e7510..5e70d24d 100644
--- a/binding/form_mapping.go
+++ b/binding/form_mapping.go
@@ -186,7 +186,10 @@ type BindUnmarshaler interface {
 func trySetCustom(val string, value reflect.Value) (isSet bool, err error) {
 	switch v := value.Addr().Interface().(type) {
 	case BindUnmarshaler:
-		return true, v.UnmarshalParam(val)
+		if err := v.UnmarshalParam(val); err != nil {
+			return true, fmt.Errorf("invalid value %q: %w", val, err)
+		}
+		return true, nil
 	}
 	return false, nil
 }
@@ -245,7 +248,10 @@ func setByForm(value reflect.Value, field reflect.StructField, form map[string][
 		}
 
 		if ok, err = trySetCustom(vs[0], value); ok {
-			return ok, err
+			if err != nil {
+				return true, fmt.Errorf("field %q: %w", field.Name, err)
+			}
+			return true, nil
 		}
 
 		if vs, err = trySplit(vs, field); err != nil {
@@ -268,7 +274,10 @@ func setByForm(value reflect.Value, field reflect.StructField, form map[string][
 		}
 
 		if ok, err = trySetCustom(vs[0], value); ok {
-			return ok, err
+			if err != nil {
+				return true, fmt.Errorf("field %q: %w", field.Name, err)
+			}
+			return true, nil
 		}
 
 		if vs, err = trySplit(vs, field); err != nil {
@@ -293,7 +302,10 @@ func setByForm(value reflect.Value, field reflect.StructField, form map[string][
 			}
 		}
 		if ok, err := trySetCustom(val, value); ok {
-			return ok, err
+			if err != nil {
+				return true, fmt.Errorf("field %q: %w", field.Name, err)
+			}
+			return true, nil
 		}
 		return true, setWithProperType(val, value, field)
 	}
@@ -461,6 +473,12 @@ func setTimeField(val string, structField reflect.StructField, value reflect.Val
 
 func setArray(vals []string, value reflect.Value, field reflect.StructField) error {
 	for i, s := range vals {
+		if ok, err := trySetCustom(s, value.Index(i)); ok {
+			if err != nil {
+				return fmt.Errorf("field %q: %w", field.Name, err)
+			}
+			continue
+		}
 		err := setWithProperType(s, value.Index(i), field)
 		if err != nil {
 			return err
diff --git a/binding/form_mapping_test.go b/binding/form_mapping_test.go
index e007573c..399874ba 100644
--- a/binding/form_mapping_test.go
+++ b/binding/form_mapping_test.go
@@ -754,3 +754,104 @@ func TestMappingEmptyValues(t *testing.T) {
 		assert.Equal(t, []int{1, 2, 3}, s.SliceCsv)
 	})
 }
+
+type testCustom struct {
+	Value string
+}
+
+func (t *testCustom) UnmarshalParam(param string) error {
+	t.Value = "prefix_" + param
+	return nil
+}
+
+func TestTrySetCustomIntegration(t *testing.T) {
+	var s struct {
+		F testCustom `form:"f"`
+	}
+
+	err := mappingByPtr(&s, formSource{"f": {"hello"}}, "form")
+	require.NoError(t, err)
+	assert.Equal(t, "prefix_hello", s.F.Value)
+}
+
+type badCustom struct{}
+
+func (b *badCustom) UnmarshalParam(s string) error {
+	return errors.New("boom")
+}
+
+func TestTrySetCustom_SingleValues(t *testing.T) {
+	t.Run("Error case", func(t *testing.T) {
+		var s struct {
+			F badCustom `form:"f"`
+		}
+
+		err := mappingByPtr(&s, formSource{"f": {"hello"}}, "form")
+		require.Error(t, err)
+		assert.Contains(t, err.Error(), "invalid value")
+	})
+
+	t.Run("Integration success", func(t *testing.T) {
+		var s struct {
+			F testCustom `form:"f"`
+		}
+
+		err := mappingByPtr(&s, formSource{"f": {"hello"}}, "form")
+		require.NoError(t, err)
+		assert.Equal(t, "prefix_hello", s.F.Value)
+	})
+
+	t.Run("Not applicable type", func(t *testing.T) {
+		var s struct {
+			N int `form:"n"`
+		}
+
+		err := mappingByPtr(&s, formSource{"n": {"42"}}, "form")
+		require.NoError(t, err)
+		assert.Equal(t, 42, s.N)
+	})
+}
+
+func TestTrySetCustom_Collections(t *testing.T) {
+	t.Run("Slice success", func(t *testing.T) {
+		var s struct {
+			F []testCustom `form:"f"`
+		}
+
+		err := mappingByPtr(&s, formSource{"f": {"one", "two"}}, "form")
+		require.NoError(t, err)
+		assert.Equal(t, "prefix_one", s.F[0].Value)
+		assert.Equal(t, "prefix_two", s.F[1].Value)
+	})
+
+	t.Run("Array success", func(t *testing.T) {
+		var s struct {
+			F [2]testCustom `form:"f"`
+		}
+
+		err := mappingByPtr(&s, formSource{"f": {"hello", "world"}}, "form")
+		require.NoError(t, err)
+		assert.Equal(t, "prefix_hello", s.F[0].Value)
+		assert.Equal(t, "prefix_world", s.F[1].Value)
+	})
+
+	t.Run("Slice error", func(t *testing.T) {
+		var s struct {
+			F []badCustom `form:"f"`
+		}
+
+		err := mappingByPtr(&s, formSource{"f": {"oops1", "oops2"}}, "form")
+		require.Error(t, err)
+		assert.Contains(t, err.Error(), "invalid value")
+	})
+
+	t.Run("Array error", func(t *testing.T) {
+		var s struct {
+			F [2]badCustom `form:"f"`
+		}
+
+		err := mappingByPtr(&s, formSource{"f": {"fail1", "fail2"}}, "form")
+		require.Error(t, err)
+		assert.Contains(t, err.Error(), "invalid value")
+	})
+}