diff --git a/cast_test.go b/cast_test.go
index d9a1479..b72bf03 100644
--- a/cast_test.go
+++ b/cast_test.go
@@ -8,6 +8,7 @@ package cast
 import (
 	"fmt"
 	"html/template"
+	"math"
 	"testing"
 	"time"
 
@@ -44,6 +45,7 @@ func TestToUintE(t *testing.T) {
 		{int64(-8), 0, true},
 		{float32(-8.31), 0, true},
 		{float64(-8.31), 0, true},
+		{math.NaN(), 0, true},
 		{"-8", 0, true},
 		{"test", 0, true},
 		{testing.T{}, 0, true},
@@ -97,6 +99,7 @@ func TestToUint64E(t *testing.T) {
 		{int64(-8), 0, true},
 		{float32(-8.31), 0, true},
 		{float64(-8.31), 0, true},
+		{math.NaN(), 0, true},
 		{"-8", 0, true},
 		{"test", 0, true},
 		{testing.T{}, 0, true},
@@ -151,6 +154,7 @@ func TestToUint32E(t *testing.T) {
 		{float64(-8.31), 0, true},
 		{"-8", 0, true},
 		// errors
+		{math.NaN(), 0, true},
 		{"test", 0, true},
 		{testing.T{}, 0, true},
 	}
@@ -203,6 +207,7 @@ func TestToUint16E(t *testing.T) {
 		{int64(-8), 0, true},
 		{float32(-8.31), 0, true},
 		{float64(-8.31), 0, true},
+		{math.NaN(), 0, true},
 		{"-8", 0, true},
 		{"test", 0, true},
 		{testing.T{}, 0, true},
@@ -256,6 +261,7 @@ func TestToUint8E(t *testing.T) {
 		{int64(-8), 0, true},
 		{float32(-8.31), 0, true},
 		{float64(-8.31), 0, true},
+		{math.NaN(), 0, true},
 		{"-8", 0, true},
 		{"test", 0, true},
 		{testing.T{}, 0, true},
@@ -302,6 +308,7 @@ func TestToIntE(t *testing.T) {
 		{"8", 8, false},
 		{nil, 0, false},
 		// errors
+		{math.NaN(), 0, true},
 		{"test", 0, true},
 		{testing.T{}, 0, true},
 	}
@@ -347,6 +354,7 @@ func TestToInt64E(t *testing.T) {
 		{"8", 8, false},
 		{nil, 0, false},
 		// errors
+		{math.NaN(), 0, true},
 		{"test", 0, true},
 		{testing.T{}, 0, true},
 	}
@@ -392,6 +400,7 @@ func TestToInt32E(t *testing.T) {
 		{"8", 8, false},
 		{nil, 0, false},
 		// errors
+		{math.NaN(), 0, true},
 		{"test", 0, true},
 		{testing.T{}, 0, true},
 	}
@@ -437,6 +446,7 @@ func TestToInt16E(t *testing.T) {
 		{"8", 8, false},
 		{nil, 0, false},
 		// errors
+		{math.NaN(), 0, true},
 		{"test", 0, true},
 		{testing.T{}, 0, true},
 	}
@@ -482,6 +492,7 @@ func TestToInt8E(t *testing.T) {
 		{"8", 8, false},
 		{nil, 0, false},
 		// errors
+		{math.NaN(), 0, true},
 		{"test", 0, true},
 		{testing.T{}, 0, true},
 	}
@@ -526,6 +537,7 @@ func TestToFloat64E(t *testing.T) {
 		{true, 1, false},
 		{false, 0, false},
 		// errors
+		{math.NaN(), 0, true},
 		{"test", 0, true},
 		{testing.T{}, 0, true},
 	}
@@ -570,6 +582,7 @@ func TestToFloat32E(t *testing.T) {
 		{true, 1, false},
 		{false, 0, false},
 		// errors
+		{math.NaN(), 0, true},
 		{"test", 0, true},
 		{testing.T{}, 0, true},
 	}
@@ -626,6 +639,7 @@ func TestToStringE(t *testing.T) {
 		{template.CSS("a"), "a", false},
 		{template.HTMLAttr("a"), "a", false},
 		// errors
+		{math.NaN(), "", true},
 		{testing.T{}, "", true},
 		{key, "", true},
 	}
@@ -725,6 +739,7 @@ func TestStringMapStringSliceE(t *testing.T) {
 		{jsonStringMapStringArray, jsonStringMapStringArrayResult, false},
 
 		// errors
+		{math.NaN(), nil, true},
 		{nil, nil, true},
 		{testing.T{}, nil, true},
 		{map[interface{}]interface{}{"foo": testing.T{}}, nil, true},
@@ -763,6 +778,7 @@ func TestToStringMapE(t *testing.T) {
 		{`{"tag": "tags", "group": true}`, map[string]interface{}{"tag": "tags", "group": true}, false},
 
 		// errors
+		{math.NaN(), nil, true},
 		{nil, nil, true},
 		{testing.T{}, nil, true},
 		{"", nil, true},
@@ -798,6 +814,7 @@ func TestToStringMapBoolE(t *testing.T) {
 		{`{"v1": true, "v2": false}`, map[string]bool{"v1": true, "v2": false}, false},
 
 		// errors
+		{math.NaN(), nil, true},
 		{nil, nil, true},
 		{testing.T{}, nil, true},
 		{"", nil, true},
@@ -836,6 +853,7 @@ func TestToStringMapIntE(t *testing.T) {
 		{`{"v1": 67, "v2": 56}`, map[string]int{"v1": 67, "v2": 56}, false},
 
 		// errors
+		{math.NaN(), nil, true},
 		{nil, nil, true},
 		{testing.T{}, nil, true},
 		{"", nil, true},
@@ -875,6 +893,7 @@ func TestToStringMapInt64E(t *testing.T) {
 		{`{"v1": 67, "v2": 56}`, map[string]int64{"v1": 67, "v2": 56}, false},
 
 		// errors
+		{math.NaN(), nil, true},
 		{nil, nil, true},
 		{testing.T{}, nil, true},
 		{"", nil, true},
@@ -919,6 +938,7 @@ func TestToStringMapStringE(t *testing.T) {
 		{jsonString, stringMapString, false},
 
 		// errors
+		{math.NaN(), nil, true},
 		{nil, nil, true},
 		{testing.T{}, nil, true},
 		{invalidJsonString, nil, true},
@@ -954,6 +974,7 @@ func TestToBoolSliceE(t *testing.T) {
 		{[]int{1, 0, 1}, []bool{true, false, true}, false},
 		{[]string{"true", "false", "true"}, []bool{true, false, true}, false},
 		// errors
+		{math.NaN(), nil, true},
 		{nil, nil, true},
 		{testing.T{}, nil, true},
 		{[]string{"foo", "bar"}, nil, true},
@@ -988,6 +1009,7 @@ func TestToIntSliceE(t *testing.T) {
 		{[]string{"2", "3"}, []int{2, 3}, false},
 		{[2]string{"2", "3"}, []int{2, 3}, false},
 		// errors
+		{math.NaN(), nil, true},
 		{nil, nil, true},
 		{testing.T{}, nil, true},
 		{[]string{"foo", "bar"}, nil, true},
@@ -1020,6 +1042,7 @@ func TestToSliceE(t *testing.T) {
 		{[]interface{}{1, 3}, []interface{}{1, 3}, false},
 		{[]map[string]interface{}{{"k1": 1}, {"k2": 2}}, []interface{}{map[string]interface{}{"k1": 1}, map[string]interface{}{"k2": 2}}, false},
 		// errors
+		{math.NaN(), nil, true},
 		{nil, nil, true},
 		{testing.T{}, nil, true},
 	}
@@ -1052,6 +1075,7 @@ func TestToStringSliceE(t *testing.T) {
 		{[]interface{}{1, 3}, []string{"1", "3"}, false},
 		{interface{}(1), []string{"1"}, false},
 		// errors
+		{math.NaN(), nil, true},
 		{nil, nil, true},
 		{testing.T{}, nil, true},
 	}
@@ -1086,6 +1110,7 @@ func TestToDurationSliceE(t *testing.T) {
 		{[]time.Duration{1, 3}, []time.Duration{1, 3}, false},
 
 		// errors
+		{math.NaN(), nil, true},
 		{nil, nil, true},
 		{testing.T{}, nil, true},
 		{[]string{"invalid"}, nil, true},
@@ -1134,6 +1159,7 @@ func TestToBoolE(t *testing.T) {
 		{-1, true, false},
 
 		// errors
+		{math.NaN(), false, true},
 		{"test", false, true},
 		{testing.T{}, false, true},
 	}
@@ -1212,6 +1238,7 @@ func TestToTimeEE(t *testing.T) {
 		{uint32(1234567890), time.Date(2009, 2, 13, 23, 31, 30, 0, time.UTC), false},
 		{time.Date(2009, 2, 13, 23, 31, 30, 0, time.UTC), time.Date(2009, 2, 13, 23, 31, 30, 0, time.UTC), false},
 		// errors
+		{math.NaN(), time.Time{}, true},
 		{"2006", time.Time{}, true},
 		{testing.T{}, time.Time{}, true},
 	}
@@ -1264,6 +1291,7 @@ func TestToDurationE(t *testing.T) {
 		{string("5m"), time.Minute * td, false},
 		{string("5h"), time.Hour * td, false},
 		// errors
+		{math.NaN(), 0, true},
 		{"test", 0, true},
 		{testing.T{}, 0, true},
 	}
diff --git a/caste.go b/caste.go
index a4859fb..a69d090 100644
--- a/caste.go
+++ b/caste.go
@@ -10,6 +10,7 @@ import (
 	"errors"
 	"fmt"
 	"html/template"
+	"math"
 	"reflect"
 	"strconv"
 	"strings"
@@ -54,7 +55,14 @@ func ToDurationE(i interface{}) (d time.Duration, err error) {
 	case int, int64, int32, int16, int8, uint, uint64, uint32, uint16, uint8:
 		d = time.Duration(ToInt64(s))
 		return
-	case float32, float64:
+	case float32:
+		d = time.Duration(ToFloat64(s))
+		return
+	case float64:
+		if math.IsNaN(s) {
+			err = fmt.Errorf("unable to cast %#v of type %T to Duration", i, i)
+			return
+		}
 		d = time.Duration(ToFloat64(s))
 		return
 	case string:
@@ -97,6 +105,9 @@ func ToFloat64E(i interface{}) (float64, error) {
 
 	switch s := i.(type) {
 	case float64:
+		if math.IsNaN(s) {
+			return 0, fmt.Errorf("unable to cast %#v of type %T to float64", i, i)
+		}
 		return s, nil
 	case float32:
 		return float64(s), nil
@@ -142,6 +153,9 @@ func ToFloat32E(i interface{}) (float32, error) {
 
 	switch s := i.(type) {
 	case float64:
+		if math.IsNaN(s) {
+			return 0, fmt.Errorf("unable to cast %#v of type %T to float32", i, i)
+		}
 		return float32(s), nil
 	case float32:
 		return s, nil
@@ -207,6 +221,9 @@ func ToInt64E(i interface{}) (int64, error) {
 	case uint8:
 		return int64(s), nil
 	case float64:
+		if math.IsNaN(s) {
+			return 0, fmt.Errorf("unable to cast %#v of type %T to int64", i, i)
+		}
 		return int64(s), nil
 	case float32:
 		return int64(s), nil
@@ -254,6 +271,9 @@ func ToInt32E(i interface{}) (int32, error) {
 	case uint8:
 		return int32(s), nil
 	case float64:
+		if math.IsNaN(s) {
+			return 0, fmt.Errorf("unable to cast %#v of type %T to int32", i, i)
+		}
 		return int32(s), nil
 	case float32:
 		return int32(s), nil
@@ -301,6 +321,9 @@ func ToInt16E(i interface{}) (int16, error) {
 	case uint8:
 		return int16(s), nil
 	case float64:
+		if math.IsNaN(s) {
+			return 0, fmt.Errorf("unable to cast %#v of type %T to int16", i, i)
+		}
 		return int16(s), nil
 	case float32:
 		return int16(s), nil
@@ -348,6 +371,9 @@ func ToInt8E(i interface{}) (int8, error) {
 	case uint8:
 		return int8(s), nil
 	case float64:
+		if math.IsNaN(s) {
+			return 0, fmt.Errorf("unable to cast %#v of type %T to int8", i, i)
+		}
 		return int8(s), nil
 	case float32:
 		return int8(s), nil
@@ -395,6 +421,9 @@ func ToIntE(i interface{}) (int, error) {
 	case uint8:
 		return int(s), nil
 	case float64:
+		if math.IsNaN(s) {
+			return 0, fmt.Errorf("unable to cast %#v of type %T to int", i, i)
+		}
 		return int(s), nil
 	case float32:
 		return int(s), nil
@@ -463,6 +492,9 @@ func ToUintE(i interface{}) (uint, error) {
 	case uint8:
 		return uint(s), nil
 	case float64:
+		if math.IsNaN(s) {
+			return 0, errNegativeNotAllowed
+		}
 		if s < 0 {
 			return 0, errNegativeNotAllowed
 		}
@@ -536,6 +568,9 @@ func ToUint64E(i interface{}) (uint64, error) {
 		}
 		return uint64(s), nil
 	case float64:
+		if math.IsNaN(s) {
+			return 0, errNegativeNotAllowed
+		}
 		if s < 0 {
 			return 0, errNegativeNotAllowed
 		}
@@ -599,6 +634,9 @@ func ToUint32E(i interface{}) (uint32, error) {
 	case uint8:
 		return uint32(s), nil
 	case float64:
+		if math.IsNaN(s) {
+			return 0, errNegativeNotAllowed
+		}
 		if s < 0 {
 			return 0, errNegativeNotAllowed
 		}
@@ -667,6 +705,9 @@ func ToUint16E(i interface{}) (uint16, error) {
 	case uint8:
 		return uint16(s), nil
 	case float64:
+		if math.IsNaN(s) {
+			return 0, errNegativeNotAllowed
+		}
 		if s < 0 {
 			return 0, errNegativeNotAllowed
 		}
@@ -735,6 +776,9 @@ func ToUint8E(i interface{}) (uint8, error) {
 	case uint8:
 		return s, nil
 	case float64:
+		if math.IsNaN(s) {
+			return 0, errNegativeNotAllowed
+		}
 		if s < 0 {
 			return 0, errNegativeNotAllowed
 		}
@@ -805,6 +849,9 @@ func ToStringE(i interface{}) (string, error) {
 	case bool:
 		return strconv.FormatBool(s), nil
 	case float64:
+		if math.IsNaN(s) {
+			return "", fmt.Errorf("unable to cast %#v of type %T to string", i, i)
+		}
 		return strconv.FormatFloat(s, 'f', -1, 64), nil
 	case float32:
 		return strconv.FormatFloat(float64(s), 'f', -1, 32), nil