diff --git a/docs/parsers/asciitable_m.md b/docs/parsers/asciitable_m.md
index be7076b6..b1ceff86 100644
--- a/docs/parsers/asciitable_m.md
+++ b/docs/parsers/asciitable_m.md
@@ -29,6 +29,9 @@ Headers (keys) are converted to snake-case and newlines between multi-line
 headers are joined with an underscore. All values are returned as strings,
 except empty strings, which are converted to None/null.
 
+> Note: table column separator characters (e.g. `|`) cannot be present
+  inside the cell data.
+
 Usage (cli):
 
     $ cat table.txt | jc --asciitable-m
diff --git a/jc/parsers/asciitable_m.py b/jc/parsers/asciitable_m.py
index 17d40a6f..b7078aa4 100644
--- a/jc/parsers/asciitable_m.py
+++ b/jc/parsers/asciitable_m.py
@@ -24,6 +24,9 @@ Headers (keys) are converted to snake-case and newlines between multi-line
 headers are joined with an underscore. All values are returned as strings,
 except empty strings, which are converted to None/null.
 
+> Note: table column separator characters (e.g. `|`) cannot be present
+  inside the cell data.
+
 Usage (cli):
 
     $ cat table.txt | jc --asciitable-m