diff --git a/doc_src/cmds/function.rst b/doc_src/cmds/function.rst
index 99a093a28..553f56eb8 100644
--- a/doc_src/cmds/function.rst
+++ b/doc_src/cmds/function.rst
@@ -28,7 +28,7 @@ The following options are available:
 
 - ``-e`` or ``--on-event EVENT_NAME`` tells fish to run this function when the specified named event is emitted. Fish internally generates named events e.g. when showing the prompt.
 
-- ``-v`` or ``--on-variable VARIABLE_NAME`` tells fish to run this function when the variable VARIABLE_NAME changes value.
+- ``-v`` or ``--on-variable VARIABLE_NAME`` tells fish to run this function when the variable VARIABLE_NAME changes value. Note that the function will not necessarily be run for each change; rather, it will be run when the variable has changed at least once.
 
 - ``-j PGID`` or ``--on-job-exit PGID`` tells fish to run this function when the job with group ID PGID exits. Instead of PGID, the string 'caller' can be specified. This is only legal when in a command substitution, and will result in the handler being triggered by the exit of the job which created this command substitution.