diff --git a/json_serialization/lexer.nim b/json_serialization/lexer.nim
index ea63a2f..48ab5b7 100644
--- a/json_serialization/lexer.nim
+++ b/json_serialization/lexer.nim
@@ -1,5 +1,5 @@
 import
-  strutils, unicode,
+  unicode,
   faststreams/input_stream, stew/objects,
   types
 
@@ -55,8 +55,6 @@ type
     strVal*: string
 
 const
-  pageSize = 4096
-
   powersOfTen = [1e0, 1e1, 1e2, 1e3, 1e4, 1e5, 1e6, 1e7, 1e8, 1e9,
                  1e10, 1e11, 1e12, 1e13, 1e14, 1e15, 1e16, 1e17, 1e18, 1e19,
                  1e20, 1e21, 1e22] # TODO: this table should be much larger
@@ -276,7 +274,7 @@ proc scanNumber(lexer: var JsonLexer) =
     lexer.tok = tkInt
     let scannedValue = lexer.scanInt()
     checkForNonPortableInt scannedValue
-    lexer.intVal = int64(scannedValue)
+    lexer.intVal = int64(scannedValue) * sign
     if lexer.stream[].eof: return
     c = lexer.stream[].peek()
     if c == '.':
diff --git a/json_serialization/reader.nim b/json_serialization/reader.nim
index f6529f0..09e97b0 100644
--- a/json_serialization/reader.nim
+++ b/json_serialization/reader.nim
@@ -144,7 +144,7 @@ iterator readObject*(r: var JsonReader, KeyType: typedesc, ValueType: typedesc):
 proc readValue*(r: var JsonReader, value: var auto) =
   mixin readValue
 
-  let tok = r.lexer.tok
+  let tok {.used.} = r.lexer.tok
 
   when value is string:
     r.requireToken tkString
diff --git a/json_serialization/writer.nim b/json_serialization/writer.nim
index f853805..ca0cb77 100644
--- a/json_serialization/writer.nim
+++ b/json_serialization/writer.nim
@@ -127,9 +127,6 @@ proc writeArray[T](w: var JsonWriter, elements: openarray[T]) =
 proc writeValue*(w: var JsonWriter, value: auto) =
   mixin enumInstanceSerializedFields, writeValue, writeFieldIMPL
 
-  template addChar(c) =
-    append c
-
   when value is JsonNode:
     append if w.hasPrettyOutput: value.pretty
            else: $value
@@ -141,11 +138,11 @@ proc writeValue*(w: var JsonWriter, value: auto) =
     else:
       writeValue(w, value[])
   elif value is string|cstring:
-    addChar '"'
+    append '"'
 
     template addPrefixSlash(c) =
-      addChar '\\'
-      addChar c
+      append '\\'
+      append c
 
     for c in value:
       case c
@@ -165,9 +162,9 @@ proc writeValue*(w: var JsonWriter, value: auto) =
         # This is potentially a bug in Nim's json module.
         append $ord(c)
       of '\\': addPrefixSlash '\\'
-      else: addChar c
+      else: append c
 
-    addChar '"'
+    append '"'
   elif value is bool:
     append if value: "true" else: "false"
   elif value is enum:
diff --git a/tests/test_serialization.nim b/tests/test_serialization.nim
index c8cb08f..917554d 100644
--- a/tests/test_serialization.nim
+++ b/tests/test_serialization.nim
@@ -26,7 +26,7 @@ type
 # properly when it's placed in another module:
 Meter.borrowSerialization int
 
-template reject(code) =
+template reject(code) {.used.} =
   static: doAssert(not compiles(code))
 
 proc `==`(lhs, rhs: Meter): bool =
@@ -45,11 +45,11 @@ proc newSimple(x: int, y: string, d: Meter): ref Simple =
   result.y = y
   result.distance = d
 
-when false:
-  # The compiler cannot handle this check at the moment
-  # {.fatal.} seems fatal even in `compiles` context
-  var invalid = Invalid(distance: Mile(100))
-  reject invalid.toJson
+var invalid = Invalid(distance: Mile(100))
+# The compiler cannot handle this check at the moment
+# {.fatal.} seems fatal even in `compiles` context
+when false: reject invalid.toJson
+else: discard invalid
 
 suite "toJson tests":
   test "encode primitives":