diff --git a/doc/manual/threads.txt b/doc/manual/threads.txt
index fc3040c87f..11380f7570 100644
--- a/doc/manual/threads.txt
+++ b/doc/manual/threads.txt
@@ -37,7 +37,7 @@ that contains GC'ed memory (``string``, ``seq``, ``ref`` or a closure) either
 directly or indirectly through a call to a GC unsafe proc.
 
 The `gcsafe`:idx: annotation can be used to mark a proc to be gcsafe,
-otherwise this property is inferred by the compiler. Note that ``noSideEfect``
+otherwise this property is inferred by the compiler. Note that ``noSideEffect``
 implies ``gcsafe``. The only way to create a thread is via ``spawn`` or
 ``createThead``. ``spawn`` is usually the preferable method. Either way
 the invoked proc must not use ``var`` parameters nor must any of its parameters