diff --git a/ratelimit_var.go b/ratelimit_var.go
index 0c310ed..d28f072 100644
--- a/ratelimit_var.go
+++ b/ratelimit_var.go
@@ -7,10 +7,20 @@ import (
 	"strings"
 	"time"
 
+	sliceutil "github.com/projectdiscovery/utils/slice"
 	stringsutil "github.com/projectdiscovery/utils/strings"
 	timeutil "github.com/projectdiscovery/utils/time"
 )
 
+var (
+	AllowedUnits       = []string{"ns", "us", "ms", "s", "m"}
+	rateLimitOptionMap map[*RateLimitMap]Options
+)
+
+func init() {
+	rateLimitOptionMap = make(map[*RateLimitMap]Options)
+}
+
 type RateLimit struct {
 	MaxCount uint
 	Duration time.Duration
@@ -25,21 +35,34 @@ func (rateLimitMap *RateLimitMap) Set(value string) error {
 	if rateLimitMap.kv == nil {
 		rateLimitMap.kv = make(map[string]RateLimit)
 	}
-	var k, v string
-	if idxSep := strings.Index(value, kvSep); idxSep > 0 {
-		k = value[:idxSep]
-		v = value[idxSep+1:]
+
+	option, ok := rateLimitOptionMap[rateLimitMap]
+	if !ok {
+		option = StringSliceOptions
+	}
+	rateLimits, err := ToStringSlice(value, option)
+	if err != nil {
+		return err
 	}
-	// note:
-	// - inserting multiple times the same key will override the previous value
-	// - empty string is legitimate value
-
-	if k != "" {
-		rateLimit, err := parseRateLimit(v)
-		if err != nil {
-			return err
+
+	for _, rateLimit := range rateLimits {
+
+		var k, v string
+		if idxSep := strings.Index(rateLimit, kvSep); idxSep > 0 {
+			k = rateLimit[:idxSep]
+			v = rateLimit[idxSep+1:]
+		}
+		// note:
+		// - inserting multiple times the same key will override the previous v
+		// - empty string is legitimate rateLimit
+
+		if k != "" {
+			rateLimit, err := parseRateLimit(v)
+			if err != nil {
+				return err
+			}
+			rateLimitMap.kv[k] = rateLimit
 		}
-		rateLimitMap.kv[k] = rateLimit
 	}
 	return nil
 }
@@ -88,6 +111,7 @@ func (flagSet *FlagSet) RateLimitMapVarP(field *RateLimitMap, long, short string
 		panic(fmt.Errorf("field cannot be nil for flag -%v", long))
 	}
 
+	rateLimitOptionMap[field] = options
 	for _, defaultItem := range defaultValue {
 		values, _ := ToStringSlice(defaultItem, options)
 		for _, value := range values {
@@ -124,9 +148,15 @@ func parseRateLimit(s string) (RateLimit, error) {
 	if err != nil {
 		return RateLimit{}, errors.New("parse error: " + err.Error())
 	}
+
 	duration, err := timeutil.ParseDuration("1" + sArr[1])
 	if err != nil {
 		return RateLimit{}, errors.New("parse error: " + err.Error())
 	}
+
+	if !sliceutil.Contains(AllowedUnits, sArr[1]) {
+		return RateLimit{}, errors.New("unit " + sArr[1] + " is not allowed")
+	}
+
 	return RateLimit{MaxCount: uint(maxCount), Duration: duration}, nil
 }
diff --git a/ratelimit_var_test.go b/ratelimit_var_test.go
index a68913e..41730cc 100644
--- a/ratelimit_var_test.go
+++ b/ratelimit_var_test.go
@@ -49,11 +49,12 @@ func TestRateLimitMapVar(t *testing.T) {
 		)
 		os.Args = []string{
 			os.Args[0],
-			"-rls", "hackertarget=10/d",
+			"-rls", "hackertarget=10/m",
 		}
 		err := flagSet.Parse()
 		assert.Nil(t, err)
-		assert.Equal(t, RateLimit{MaxCount: 10, Duration: time.Hour * 24}, rateLimitMap.AsMap()["hackertarget"])
+		assert.Equal(t, RateLimit{MaxCount: 10, Duration: time.Minute}, rateLimitMap.AsMap()["hackertarget"])
+
 		tearDown(t.Name())
 	})
 
@@ -65,11 +66,12 @@ func TestRateLimitMapVar(t *testing.T) {
 		)
 		os.Args = []string{
 			os.Args[0],
-			"-rls", "hackertarget=10/d",
+			"-rls", "hackertarget=1/s,github=1/ms",
 		}
 		err := flagSet.Parse()
 		assert.Nil(t, err)
-		assert.Equal(t, RateLimit{MaxCount: 10, Duration: time.Hour * 24}, rateLimitMap.AsMap()["hackertarget"])
+		assert.Equal(t, RateLimit{MaxCount: 1, Duration: time.Second}, rateLimitMap.AsMap()["hackertarget"])
+		assert.Equal(t, RateLimit{MaxCount: 1, Duration: time.Millisecond}, rateLimitMap.AsMap()["github"])
 		tearDown(t.Name())
 	})