diff --git a/lib/pure/bitops.nim b/lib/pure/bitops.nim
index ba4fc28bbb..3d2285cf9e 100644
--- a/lib/pure/bitops.nim
+++ b/lib/pure/bitops.nim
@@ -130,6 +130,9 @@ when defined(nimHasalignOf):
 
   macro setBits*(v: typed, bits: varargs[typed]): untyped =
     ## Returns ``v``, with the bits at positions ``bits`` set to 1
+    ##
+    ## **Note:**
+    ## * ``v`` must be `var` variable.
     runnableExamples:
       var v = 0b0000_0011'u8
       v.setBits(3, 5, 7)
@@ -142,6 +145,9 @@ when defined(nimHasalignOf):
 
   macro clearBits*(v: typed, bits: varargs[typed]): untyped =
     ## Returns ``v``, with the bits at positions ``bits`` set to 0
+    ##
+    ## **Note:**
+    ## * ``v`` must be `var` variable.
     runnableExamples:
       var v = 0b1111_1111'u8
       v.clearBits(1, 3, 5, 7)
@@ -154,6 +160,9 @@ when defined(nimHasalignOf):
 
   macro flipBits*(v: typed, bits: varargs[typed]): untyped =
     ## Returns ``v``, with the bits at positions ``bits`` set to 0
+    ##
+    ## **Note:**
+    ## * ``v`` must be `var` variable.
     runnableExamples:
       var v = 0b0000_1111'u8
       v.flipBits(1, 3, 5, 7)