diff --git a/json_serialization/lexer.nim b/json_serialization/lexer.nim
index 3a79e69..ea63a2f 100644
--- a/json_serialization/lexer.nim
+++ b/json_serialization/lexer.nim
@@ -276,7 +276,7 @@ proc scanNumber(lexer: var JsonLexer) =
     lexer.tok = tkInt
     let scannedValue = lexer.scanInt()
     checkForNonPortableInt scannedValue
-    lexer.intVal = int(scannedValue)
+    lexer.intVal = int64(scannedValue)
     if lexer.stream[].eof: return
     c = lexer.stream[].peek()
     if c == '.':
diff --git a/tests/test_lexer.nim b/tests/test_lexer.nim
index f85c159..87ed2ae 100644
--- a/tests/test_lexer.nim
+++ b/tests/test_lexer.nim
@@ -40,6 +40,10 @@ suite "lexer tests":
     expectedToken tkInt,      lexer.intVal == 190
     expectedToken tkEof
 
+  lexerTest "int64 literal",  "3568257348920230622":
+    expectedToken tkInt,      lexer.intVal == 3568257348920230622'i64
+    expectedToken tkEof
+
   lexerTest "float literal",  ".340":
     expectedToken tkFloat,    lexer.floatVal =~ 0.340
     expectedToken tkEof
diff --git a/tests/utils.nim b/tests/utils.nim
index d8d7307..565c2f9 100644
--- a/tests/utils.nim
+++ b/tests/utils.nim
@@ -3,7 +3,7 @@ import
 
 proc dedent*(s: string): string =
   var s = s.strip(leading = false)
-  var minIndent = 99999999999
+  var minIndent = high(int)
   for l in s.splitLines:
     let indent = count(l, ' ')
     if indent == 0: continue