diff --git a/src/sync/atomic/doc.go b/src/sync/atomic/doc.go
index a7d5b46288..bb3b8f673e 100644
--- a/src/sync/atomic/doc.go
+++ b/src/sync/atomic/doc.go
@@ -46,8 +46,9 @@ import (
 //
 // On non-Linux ARM, the 64-bit functions use instructions unavailable before the ARMv6k core.
 //
-// On ARM, 386, and 32-bit MIPS, it is the caller's responsibility
-// to arrange for 64-bit alignment of 64-bit words accessed atomically.
+// On ARM, 386, and 32-bit MIPS, it is the caller's responsibility to arrange
+// for 64-bit alignment of 64-bit words accessed atomically via the primitive
+// atomic functions (types Int64 and Uint64 are automatically aligned).
 // The first word in a variable or in an allocated struct, array, or slice can
 // be relied upon to be 64-bit aligned.