diff --git a/flag_test.go b/flag_test.go
index 0dd8654..1ccb639 100644
--- a/flag_test.go
+++ b/flag_test.go
@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"os"
 	"reflect"
+	"regexp"
 	"runtime"
 	"strings"
 	"testing"
@@ -31,57 +32,57 @@ func TestBoolFlagHelpOutput(t *testing.T) {
 
 func TestFlagsFromEnv(t *testing.T) {
 	var flagTests = []struct {
-		input  string
-		output interface{}
-		flag   Flag
-		err    error
+		input     string
+		output    interface{}
+		flag      Flag
+		errRegexp string
 	}{
-		{"", false, BoolFlag{Name: "debug", EnvVar: "DEBUG"}, nil},
-		{"1", true, BoolFlag{Name: "debug", EnvVar: "DEBUG"}, nil},
-		{"false", false, BoolFlag{Name: "debug", EnvVar: "DEBUG"}, nil},
-		{"foobar", true, BoolFlag{Name: "debug", EnvVar: "DEBUG"}, fmt.Errorf(`could not parse foobar as bool value for flag debug: strconv.ParseBool: parsing "foobar": invalid syntax`)},
+		{"", false, BoolFlag{Name: "debug", EnvVar: "DEBUG"}, ""},
+		{"1", true, BoolFlag{Name: "debug", EnvVar: "DEBUG"}, ""},
+		{"false", false, BoolFlag{Name: "debug", EnvVar: "DEBUG"}, ""},
+		{"foobar", true, BoolFlag{Name: "debug", EnvVar: "DEBUG"}, fmt.Sprintf(`could not parse foobar as bool value for flag debug: .*`)},
 
-		{"", false, BoolTFlag{Name: "debug", EnvVar: "DEBUG"}, nil},
-		{"1", true, BoolTFlag{Name: "debug", EnvVar: "DEBUG"}, nil},
-		{"false", false, BoolTFlag{Name: "debug", EnvVar: "DEBUG"}, nil},
-		{"foobar", true, BoolTFlag{Name: "debug", EnvVar: "DEBUG"}, fmt.Errorf(`could not parse foobar as bool value for flag debug: strconv.ParseBool: parsing "foobar": invalid syntax`)},
+		{"", false, BoolTFlag{Name: "debug", EnvVar: "DEBUG"}, ""},
+		{"1", true, BoolTFlag{Name: "debug", EnvVar: "DEBUG"}, ""},
+		{"false", false, BoolTFlag{Name: "debug", EnvVar: "DEBUG"}, ""},
+		{"foobar", true, BoolTFlag{Name: "debug", EnvVar: "DEBUG"}, fmt.Sprintf(`could not parse foobar as bool value for flag debug: .*`)},
 
-		{"1s", 1 * time.Second, DurationFlag{Name: "time", EnvVar: "TIME"}, nil},
-		{"foobar", false, DurationFlag{Name: "time", EnvVar: "TIME"}, fmt.Errorf(`could not parse foobar as duration for flag time: time: invalid duration foobar`)},
+		{"1s", 1 * time.Second, DurationFlag{Name: "time", EnvVar: "TIME"}, ""},
+		{"foobar", false, DurationFlag{Name: "time", EnvVar: "TIME"}, fmt.Sprintf(`could not parse foobar as duration for flag time: .*`)},
 
-		{"1.2", 1.2, Float64Flag{Name: "seconds", EnvVar: "SECONDS"}, nil},
-		{"1", 1.0, Float64Flag{Name: "seconds", EnvVar: "SECONDS"}, nil},
-		{"foobar", 0, Float64Flag{Name: "seconds", EnvVar: "SECONDS"}, fmt.Errorf(`could not parse foobar as float64 value for flag seconds: strconv.ParseFloat: parsing "foobar": invalid syntax`)},
+		{"1.2", 1.2, Float64Flag{Name: "seconds", EnvVar: "SECONDS"}, ""},
+		{"1", 1.0, Float64Flag{Name: "seconds", EnvVar: "SECONDS"}, ""},
+		{"foobar", 0, Float64Flag{Name: "seconds", EnvVar: "SECONDS"}, fmt.Sprintf(`could not parse foobar as float64 value for flag seconds: .*`)},
 
-		{"1", int64(1), Int64Flag{Name: "seconds", EnvVar: "SECONDS"}, nil},
-		{"1.2", 0, Int64Flag{Name: "seconds", EnvVar: "SECONDS"}, fmt.Errorf(`could not parse 1.2 as int value for flag seconds: strconv.ParseInt: parsing "1.2": invalid syntax`)},
-		{"foobar", 0, Int64Flag{Name: "seconds", EnvVar: "SECONDS"}, fmt.Errorf(`could not parse foobar as int value for flag seconds: strconv.ParseInt: parsing "foobar": invalid syntax`)},
+		{"1", int64(1), Int64Flag{Name: "seconds", EnvVar: "SECONDS"}, ""},
+		{"1.2", 0, Int64Flag{Name: "seconds", EnvVar: "SECONDS"}, fmt.Sprintf(`could not parse 1.2 as int value for flag seconds: .*`)},
+		{"foobar", 0, Int64Flag{Name: "seconds", EnvVar: "SECONDS"}, fmt.Sprintf(`could not parse foobar as int value for flag seconds: .*`)},
 
-		{"1", 1, IntFlag{Name: "seconds", EnvVar: "SECONDS"}, nil},
-		{"1.2", 0, IntFlag{Name: "seconds", EnvVar: "SECONDS"}, fmt.Errorf(`could not parse 1.2 as int value for flag seconds: strconv.ParseInt: parsing "1.2": invalid syntax`)},
-		{"foobar", 0, IntFlag{Name: "seconds", EnvVar: "SECONDS"}, fmt.Errorf(`could not parse foobar as int value for flag seconds: strconv.ParseInt: parsing "foobar": invalid syntax`)},
+		{"1", 1, IntFlag{Name: "seconds", EnvVar: "SECONDS"}, ""},
+		{"1.2", 0, IntFlag{Name: "seconds", EnvVar: "SECONDS"}, fmt.Sprintf(`could not parse 1.2 as int value for flag seconds: .*`)},
+		{"foobar", 0, IntFlag{Name: "seconds", EnvVar: "SECONDS"}, fmt.Sprintf(`could not parse foobar as int value for flag seconds: .*`)},
 
-		{"1,2", IntSlice{1, 2}, IntSliceFlag{Name: "seconds", EnvVar: "SECONDS"}, nil},
-		{"1.2,2", IntSlice{}, IntSliceFlag{Name: "seconds", EnvVar: "SECONDS"}, fmt.Errorf(`could not parse 1.2,2 as int slice value for flag seconds: strconv.ParseInt: parsing "1.2": invalid syntax`)},
-		{"foobar", IntSlice{}, IntSliceFlag{Name: "seconds", EnvVar: "SECONDS"}, fmt.Errorf(`could not parse foobar as int slice value for flag seconds: strconv.ParseInt: parsing "foobar": invalid syntax`)},
+		{"1,2", IntSlice{1, 2}, IntSliceFlag{Name: "seconds", EnvVar: "SECONDS"}, ""},
+		{"1.2,2", IntSlice{}, IntSliceFlag{Name: "seconds", EnvVar: "SECONDS"}, fmt.Sprintf(`could not parse 1.2,2 as int slice value for flag seconds: .*`)},
+		{"foobar", IntSlice{}, IntSliceFlag{Name: "seconds", EnvVar: "SECONDS"}, fmt.Sprintf(`could not parse foobar as int slice value for flag seconds: .*`)},
 
-		{"1,2", Int64Slice{1, 2}, Int64SliceFlag{Name: "seconds", EnvVar: "SECONDS"}, nil},
-		{"1.2,2", Int64Slice{}, Int64SliceFlag{Name: "seconds", EnvVar: "SECONDS"}, fmt.Errorf(`could not parse 1.2,2 as int64 slice value for flag seconds: strconv.ParseInt: parsing "1.2": invalid syntax`)},
-		{"foobar", Int64Slice{}, Int64SliceFlag{Name: "seconds", EnvVar: "SECONDS"}, fmt.Errorf(`could not parse foobar as int64 slice value for flag seconds: strconv.ParseInt: parsing "foobar": invalid syntax`)},
+		{"1,2", Int64Slice{1, 2}, Int64SliceFlag{Name: "seconds", EnvVar: "SECONDS"}, ""},
+		{"1.2,2", Int64Slice{}, Int64SliceFlag{Name: "seconds", EnvVar: "SECONDS"}, fmt.Sprintf(`could not parse 1.2,2 as int64 slice value for flag seconds: .*`)},
+		{"foobar", Int64Slice{}, Int64SliceFlag{Name: "seconds", EnvVar: "SECONDS"}, fmt.Sprintf(`could not parse foobar as int64 slice value for flag seconds: .*`)},
 
-		{"foo", "foo", StringFlag{Name: "name", EnvVar: "NAME"}, nil},
+		{"foo", "foo", StringFlag{Name: "name", EnvVar: "NAME"}, ""},
 
-		{"foo,bar", StringSlice{"foo", "bar"}, StringSliceFlag{Name: "names", EnvVar: "NAMES"}, nil},
+		{"foo,bar", StringSlice{"foo", "bar"}, StringSliceFlag{Name: "names", EnvVar: "NAMES"}, ""},
 
-		{"1", uint(1), UintFlag{Name: "seconds", EnvVar: "SECONDS"}, nil},
-		{"1.2", 0, UintFlag{Name: "seconds", EnvVar: "SECONDS"}, fmt.Errorf(`could not parse 1.2 as uint value for flag seconds: strconv.ParseUint: parsing "1.2": invalid syntax`)},
-		{"foobar", 0, UintFlag{Name: "seconds", EnvVar: "SECONDS"}, fmt.Errorf(`could not parse foobar as uint value for flag seconds: strconv.ParseUint: parsing "foobar": invalid syntax`)},
+		{"1", uint(1), UintFlag{Name: "seconds", EnvVar: "SECONDS"}, ""},
+		{"1.2", 0, UintFlag{Name: "seconds", EnvVar: "SECONDS"}, fmt.Sprintf(`could not parse 1.2 as uint value for flag seconds: .*`)},
+		{"foobar", 0, UintFlag{Name: "seconds", EnvVar: "SECONDS"}, fmt.Sprintf(`could not parse foobar as uint value for flag seconds: .*`)},
 
-		{"1", uint64(1), Uint64Flag{Name: "seconds", EnvVar: "SECONDS"}, nil},
-		{"1.2", 0, Uint64Flag{Name: "seconds", EnvVar: "SECONDS"}, fmt.Errorf(`could not parse 1.2 as uint64 value for flag seconds: strconv.ParseUint: parsing "1.2": invalid syntax`)},
-		{"foobar", 0, Uint64Flag{Name: "seconds", EnvVar: "SECONDS"}, fmt.Errorf(`could not parse foobar as uint64 value for flag seconds: strconv.ParseUint: parsing "foobar": invalid syntax`)},
+		{"1", uint64(1), Uint64Flag{Name: "seconds", EnvVar: "SECONDS"}, ""},
+		{"1.2", 0, Uint64Flag{Name: "seconds", EnvVar: "SECONDS"}, fmt.Sprintf(`could not parse 1.2 as uint64 value for flag seconds: .*`)},
+		{"foobar", 0, Uint64Flag{Name: "seconds", EnvVar: "SECONDS"}, fmt.Sprintf(`could not parse foobar as uint64 value for flag seconds: .*`)},
 
-		{"foo,bar", &Parser{"foo", "bar"}, GenericFlag{Name: "names", Value: &Parser{}, EnvVar: "NAMES"}, nil},
+		{"foo,bar", &Parser{"foo", "bar"}, GenericFlag{Name: "names", Value: &Parser{}, EnvVar: "NAMES"}, ""},
 	}
 
 	for _, test := range flagTests {
@@ -98,8 +99,19 @@ func TestFlagsFromEnv(t *testing.T) {
 		}
 
 		err := a.Run([]string{"run"})
-		if !reflect.DeepEqual(test.err, err) {
-			t.Errorf("expected error %s, got error %s", test.err, err)
+
+		if test.errRegexp != "" {
+			if err == nil {
+				t.Errorf("expected error to match %s, got none", test.errRegexp)
+			} else {
+				if matched, _ := regexp.MatchString(test.errRegexp, err.Error()); !matched {
+					t.Errorf("expected error to match %s, got error %s", test.errRegexp, err)
+				}
+			}
+		} else {
+			if err != nil && test.errRegexp == "" {
+				t.Errorf("expected no error got %s", err)
+			}
 		}
 	}
 }