Trivial  typo fix in arch.h docs
diff --git a/src/include/lwip/arch.h b/src/include/lwip/arch.h
index 940ab62..4e921fc 100644
--- a/src/include/lwip/arch.h
+++ b/src/include/lwip/arch.h
@@ -50,7 +50,7 @@
 /**
  * @defgroup compiler_abstraction Compiler/platform abstraction
  * @ingroup sys_layer
- * All defines related to this section must not be places in lwipopts.h,
+ * All defines related to this section must not be placed in lwipopts.h,
  * but in arch/cc.h!
  * @{
  */