diff --git a/Sources/IntExtensions.swift b/Sources/IntExtensions.swift
index c3b53e3f..7271db8f 100644
--- a/Sources/IntExtensions.swift
+++ b/Sources/IntExtensions.swift
@@ -26,7 +26,7 @@ import Foundation
         }
 
         func addingReportingOverflow(other: Int) -> (partialValue: Int, overflow: ArithmeticOverflow) {
-            let (exponent, overflow) = Int.addWithOverflow(self, other)
+            let (exponent, overflow) = self.addingReportingOverflow(other)
             return (exponent, ArithmeticOverflow(overflow))
         }
     }
diff --git a/Sources/JSONParser.swift b/Sources/JSONParser.swift
index 61b6899d..ca516077 100644
--- a/Sources/JSONParser.swift
+++ b/Sources/JSONParser.swift
@@ -455,13 +455,14 @@ public struct JSONParser {
                 parser.parseLeadingZero()
 
             case .preDecimalDigits:
+                let parserStart = parser.start
                 try parser.parsePreDecimalDigits { c in
                     guard case let (exponent, .none) = 10.multipliedReportingOverflow(other: value) else {
-                        throw InternalError.numberOverflow(offset: parser.start)
+                        throw InternalError.numberOverflow(offset: parserStart)
                     }
                     
                     guard case let (newValue, .none) = exponent.addingReportingOverflow(other: Int(c - Literal.zero)) else {
-                        throw InternalError.numberOverflow(offset: parser.start)
+                        throw InternalError.numberOverflow(offset: parserStart)
                     }
                     
                     value = newValue