diff --git a/typecheck/builtin/int_test.go b/typecheck/builtin/int_test.go
index 63dc04e..0461847 100644
--- a/typecheck/builtin/int_test.go
+++ b/typecheck/builtin/int_test.go
@@ -92,6 +92,15 @@ func TestInt_Values(t *testing.T) {
 		// we cannot just add 1 because of how precision works
 		{float64(math.MaxInt64 + 1024 + 2), false},
 
+		// json number
+		{fmt.Sprintf("%f", float64(math.MinInt64-1024-1)), false},
+		{fmt.Sprintf("%d", math.MinInt64), true},
+		{"-1", true},
+		{"0", true},
+		{"1", true},
+		{fmt.Sprintf("%d", math.MaxInt64), true},
+		{fmt.Sprintf("%f", float64(math.MaxInt64+1024+2)), false},
+
 		{"string", false},
 		{[]byte("bytes"), false},
 		{-0.1, false},
diff --git a/typecheck/builtin/uint.go b/typecheck/builtin/uint.go
index 2eb7914..fbbaf38 100644
--- a/typecheck/builtin/uint.go
+++ b/typecheck/builtin/uint.go
@@ -1,6 +1,9 @@
 package builtin
 
 import (
+	"encoding/json"
+	"math"
+
 	"git.xdrm.io/go/aicra/typecheck"
 )
 
@@ -19,12 +22,40 @@ func (Uint) Checker(typeName string) typecheck.CheckerFunc {
 		return nil
 	}
 	return func(value interface{}) bool {
-		cast, isFloat := readFloat(value)
+		_, isInt := readUint(value)
+
+		return isInt
+	}
+}
+
+// readUint tries to read a serialized uint and returns whether it succeeded.
+func readUint(value interface{}) (uint, bool) {
+	switch cast := value.(type) {
+
+	case int:
+		return uint(cast), cast >= 0
+
+	case uint:
+		return cast, true
+
+	case float64:
+		uintVal := uint(cast)
+		overflows := cast < 0 || cast > math.MaxUint64
+		return uintVal, cast == float64(uintVal) && !overflows
+
+		// serialized string -> try to convert to float
+	case string:
+		num := json.Number(cast)
+		floatVal, err := num.Float64()
+		if err != nil {
+			return 0, false
+		}
+		overflows := floatVal < 0 || floatVal > math.MaxUint64
+		return uint(floatVal), !overflows
+
+		// unknown type
+	default:
+		return 0, false
 
-		if !isFloat {
-			return false
-		}
-
-		return cast >= 0 && cast == float64(int(cast))
 	}
 }
diff --git a/typecheck/builtin/uint_test.go b/typecheck/builtin/uint_test.go
new file mode 100644
index 0000000..c1d26aa
--- /dev/null
+++ b/typecheck/builtin/uint_test.go
@@ -0,0 +1,122 @@
+package builtin_test
+
+import (
+	"fmt"
+	"math"
+	"testing"
+
+	"git.xdrm.io/go/aicra/typecheck/builtin"
+)
+
+func TestUint_New(t *testing.T) {
+	t.Parallel()
+
+	inst := interface{}(builtin.NewUint())
+
+	switch cast := inst.(type) {
+	case *builtin.Uint:
+		return
+	default:
+		t.Errorf("expect %T ; got %T", &builtin.Uint{}, cast)
+	}
+}
+
+func TestUint_AvailableTypes(t *testing.T) {
+	t.Parallel()
+
+	inst := builtin.NewUint()
+
+	tests := []struct {
+		Type    string
+		Handled bool
+	}{
+		{"uint", true},
+		{"Uint", false},
+		{"UINT", false},
+		{" uint", false},
+		{"uint ", false},
+		{" uint ", false},
+	}
+
+	for _, test := range tests {
+		t.Run(test.Type, func(t *testing.T) {
+			checker := inst.Checker(test.Type)
+			if checker == nil {
+				if test.Handled {
+					t.Errorf("expect %q to be handled", test.Type)
+					t.Fail()
+				}
+				return
+			}
+
+			if !test.Handled {
+				t.Errorf("expect %q NOT to be handled", test.Type)
+				t.Fail()
+			}
+		})
+	}
+
+}
+
+func TestUint_Values(t *testing.T) {
+	t.Parallel()
+
+	const typeName = "uint"
+
+	checker := builtin.NewUint().Checker(typeName)
+	if checker == nil {
+		t.Errorf("expect %q to be handled", typeName)
+		t.Fail()
+	}
+
+	tests := []struct {
+		Value interface{}
+		Valid bool
+	}{
+		{uint(0), true},
+		{uint(math.MaxInt64), true},
+		{uint(math.MaxUint64), true},
+		{-1, false},
+		{-math.MaxInt64, false},
+
+		{float64(math.MinInt64), false},
+		{float64(0), true},
+		{float64(math.MaxInt64), true},
+		// we cannot just compare because of how precision works
+		{float64(math.MaxUint64 - 1024), true},
+		{float64(math.MaxUint64 + 1), false},
+
+		// json number
+		{fmt.Sprintf("%d", math.MinInt64), false},
+		{"-1", false},
+		{"0", true},
+		{"1", true},
+		{fmt.Sprintf("%d", math.MaxInt64), true},
+		{fmt.Sprintf("%d", uint(math.MaxUint64)), true},
+		// strane offset because of how precision works
+		{fmt.Sprintf("%f", float64(math.MaxUint64+1024*3)), false},
+
+		{"string", false},
+		{[]byte("bytes"), false},
+		{-0.1, false},
+		{0.1, false},
+		{nil, false},
+	}
+
+	for i, test := range tests {
+		t.Run(fmt.Sprintf("%d", i), func(t *testing.T) {
+			if checker(test.Value) {
+				if !test.Valid {
+					t.Errorf("expect value to be invalid")
+					t.Fail()
+				}
+				return
+			}
+			if test.Valid {
+				t.Errorf("expect value to be valid")
+				t.Fail()
+			}
+		})
+	}
+
+}