diff --git a/topdown/parse_bytes.go b/topdown/parse_bytes.go
index 9bea175e20..817edd5ee3 100644
--- a/topdown/parse_bytes.go
+++ b/topdown/parse_bytes.go
@@ -14,18 +14,16 @@ import (
 	"github.com/open-policy-agent/opa/topdown/builtins"
 )
 
-type multiplier int
-
 const (
-	none multiplier = 1
-	kb              = 1000
-	ki              = 1024
-	mb              = kb * 1000
-	mi              = ki * 1024
-	gb              = mb * 1000
-	gi              = mi * 1024
-	tb              = gb * 1000
-	ti              = gi * 1024
+	none int64 = 1
+	kb         = 1000
+	ki         = 1024
+	mb         = kb * 1000
+	mi         = ki * 1024
+	gb         = mb * 1000
+	gi         = mi * 1024
+	tb         = gb * 1000
+	ti         = gi * 1024
 )
 
 // The rune values for 0..9 as well as the period symbol (for parsing floats)
@@ -46,7 +44,7 @@ var (
 )
 
 func builtinNumBytes(a ast.Value) (ast.Value, error) {
-	var m multiplier
+	var m int64
 
 	raw, err := builtins.StringOperand(a, 1)
 	if err != nil {
@@ -88,14 +86,14 @@ func builtinNumBytes(a ast.Value) (ast.Value, error) {
 		return nil, errUnitNotRecognized(unitStr)
 	}
 
-	num, err := strconv.Atoi(numStr)
+	num, err := strconv.ParseInt(numStr, 10, 64)
 	if err != nil {
 		return nil, errIntConv
 	}
 
-	total := num * int(m)
+	total := num * m
 
-	return builtins.IntToNumber(big.NewInt(int64(total))), nil
+	return builtins.IntToNumber(big.NewInt(total)), nil
 }
 
 // Makes the string lower case and removes spaces and quotation marks