diff --git a/core/src/main/scala/com/eed3si9n/jarjarabrams/scalasig/ScalaSigAnnotationVisitor.scala b/core/src/main/scala/com/eed3si9n/jarjarabrams/scalasig/ScalaSigAnnotationVisitor.scala
index bdc262c..ad2b511 100644
--- a/core/src/main/scala/com/eed3si9n/jarjarabrams/scalasig/ScalaSigAnnotationVisitor.scala
+++ b/core/src/main/scala/com/eed3si9n/jarjarabrams/scalasig/ScalaSigAnnotationVisitor.scala
@@ -24,6 +24,7 @@ class ScalaSigAnnotationVisitor(
     cv: ClassVisitor,
     renamer: String => Option[String]
 ) extends AnnotationVisitor(Opcodes.ASM7) {
+  import ScalaSigAnnotationVisitor._
 
   private val MaxStringSizeInBytes = 65535
   private val annotationBytes: ByteArrayOutputStream = new ByteArrayOutputStream()
@@ -65,32 +66,15 @@ class ScalaSigAnnotationVisitor(
       // Encode as ScalaLongSignature containing an array of strings
       val av = cv.visitAnnotation("Lscala/reflect/ScalaLongSignature;", visible)
 
-      def nextChunk(from: Int): Array[Char] = {
-        if (from == chars.length) {
-          Array.empty
-        } else {
-          var size = 0
-          var index = 0
-
-          while (size < MaxStringSizeInBytes && from + index < chars.length) {
-            val c = chars(from + index)
-            size += (if (c == 0) 2 else 1)
-            index += 1
-          }
-
-          chars.slice(from, from + index)
-        }
-      }
-
       // Write the array of strings as chunks of max MaxStringSizeInBytes bytes
       val arrayVisitor = av.visitArray("bytes")
 
       var offset = 0
-      var chunk = nextChunk(offset)
+      var chunk = nextChunk(chars, offset, MaxStringSizeInBytes)
       while (chunk.nonEmpty) {
         arrayVisitor.visit("bytes", new String(chunk))
         offset += chunk.length
-        chunk = nextChunk(offset)
+        chunk = nextChunk(chars, offset, MaxStringSizeInBytes)
       }
       arrayVisitor.visitEnd()
 
@@ -127,3 +111,22 @@ class ScalaSigAnnotationVisitor(
     ca
   }
 }
+
+object ScalaSigAnnotationVisitor {
+  def nextChunk(chars: Array[Char], from: Int, maxBytes: Int): Array[Char] = {
+    if (from == chars.length) {
+      Array.empty
+    } else {
+      var size = 0
+      var index = 0
+
+      while (size < maxBytes && from + index < chars.length) {
+        val c = chars(from + index)
+        size += (if (c == 0) 2 else 1)
+        if (size <= maxBytes) index += 1
+      }
+
+      chars.slice(from, from + index)
+    }
+  }
+}
diff --git a/core/src/test/scala/testpkg/ScalaSigAnnotationVisitorSpec.scala b/core/src/test/scala/testpkg/ScalaSigAnnotationVisitorSpec.scala
new file mode 100644
index 0000000..d9c3fae
--- /dev/null
+++ b/core/src/test/scala/testpkg/ScalaSigAnnotationVisitorSpec.scala
@@ -0,0 +1,25 @@
+package testpkg
+
+import verify._
+import com.eed3si9n.jarjarabrams.scalasig.ScalaSigAnnotationVisitor
+
+object ScalaSigAnnotationVisitorSpec extends BasicTestSuite {
+  test("nextChunk") {
+    import ScalaSigAnnotationVisitor.nextChunk
+
+    val chars1 = Array('a', 'b', 'c', 'd', 'e', 'f', 'g', 'h')
+    assert(nextChunk(chars1, chars1.length, 3).toSeq.isEmpty)
+    assert(nextChunk(chars1, 0, 3).toSeq == Seq('a', 'b', 'c'))
+    assert(nextChunk(chars1, 3, 3).toSeq == Seq('d', 'e', 'f'))
+    assert(nextChunk(chars1, 6, 3).toSeq == Seq('g', 'h'))
+
+    val chars2 = Array('\u0000', 'a', 'b', 'c', 'd', 'e', '\u0000', 'g', '\u0000')
+    assert(nextChunk(chars2, 0, 3).toSeq == Seq('\u0000', 'a'))
+    assert(nextChunk(chars2, 2, 3).toSeq == Seq('b', 'c', 'd'))
+    assert(nextChunk(chars2, 5, 3).toSeq == Seq('e', '\u0000'))
+    assert(nextChunk(chars2, 5, 2).toSeq == Seq('e'))
+    assert(nextChunk(chars2, 7, 3).toSeq == Seq('g', '\u0000'))
+    assert(nextChunk(chars2, 7, 2).toSeq == Seq('g'))
+    assert(nextChunk(chars2, 8, 2).toSeq == Seq('\u0000'))
+  }
+}