diff --git a/README.md b/README.md
index e14d00d..5c7f07e 100644
--- a/README.md
+++ b/README.md
@@ -155,8 +155,11 @@ proc toData(data: var openArray[byte]; pos: var int; input: T)
 proc byteSize(x: T): int {.inline.} ## The size that will be consumed by the serialized type in bytes.
 ```
 
-This is only necessary for objects that contain raw pointers. `mutate`, `default` and `==`
-must also be defined. `drchaos/common` exports read/write procs that assist with this task.
+This is only necessary for objects that contain raw pointers.
+`drchaos/common` exports read/write procs that assist with this task.
+
+`mutate`, `default` and `==` must also be defined.
+Containers also need `mitems` or `mpairs` iterators.
 
 ### Dos and don'ts
 
diff --git a/drchaos/mutator.nim b/drchaos/mutator.nim
index bde3da2..cee313b 100644
--- a/drchaos/mutator.nim
+++ b/drchaos/mutator.nim
@@ -619,10 +619,12 @@ template mutatorImpl*(target, mutator, typ: untyped) =
     reset(cached)
     setLen(buffer, 1)
 
-  proc testOneInputImpl(data: openArray[byte]) =
+  proc testOneInputImpl(data: openArray[byte]): cint =
     if data.len > 1: # Ignore '\n' passed by LibFuzzer.
       getInput(data)
       FuzzTarget(target)(cached)
+      result = 0
+    else: result = -1
 
   proc customMutatorImpl(data: openArray[byte]; maxLen: int; seed: int64): int {.nosan.} =
     var r = initRand(seed)
@@ -639,9 +641,8 @@ template mutatorImpl*(target, mutator, typ: untyped) =
       result = data.len
 
   proc LLVMFuzzerTestOneInput(data: ptr UncheckedArray[byte]; len: int): cint {.exportc.} =
-    result = 0
     try:
-      testOneInputImpl(toOpenArray(data, 0, len-1))
+      result = testOneInputImpl(toOpenArray(data, 0, len-1))
     finally:
       # Call Nim's compiler api to report unhandled exceptions. See: Nim#18215
       when compileOption("exceptions", "goto"):
diff --git a/examples/fuzz_graph.nim b/examples/fuzz_graph.nim
index c24e0b2..798e4b6 100644
--- a/examples/fuzz_graph.nim
+++ b/examples/fuzz_graph.nim
@@ -44,7 +44,7 @@ proc deleteEdge*[T](x: var Graph[T]; `from`, to: Natural) =
     if (let toNodeIdx = fromNode.edges.find(to.NodeIdx); toNodeIdx != -1):
       template toNode: untyped = fromNode.edges[toNodeIdx]
       fromNode.edges.delete(toNodeIdx)
-      #x.deleteNode(toNode.int) #sneaky bug?
+      x.deleteNode(toNode.int) # sneaky bug
 
 when defined(runFuzzTests) and isMainModule:
   import std/random, drchaos/[mutator, common]
@@ -100,7 +100,7 @@ when defined(runFuzzTests) and isMainModule:
         x.nodes[7].edges.len == 0:
       doAssert false
     # Here you could call library functions and check invariants.
-    # Such as when removing edges, the number of nodes remains the same.
+    # Such as when removing edges, the number of nodes should remain the same.
     #var x = x
     #let oldLen = x.nodes.len
     #x.deleteEdge(1, 2)