diff --git a/src/configoptions.cpp b/src/configoptions.cpp
index e7ffbfe..56506e9 100644
--- a/src/configoptions.cpp
+++ b/src/configoptions.cpp
@@ -1033,8 +1033,10 @@ void addConfigOptions(Config *cfg)
                  "is the value of the INPUT_FILTER tag, and <input-file> is the name of an\n"
                  "input file. Doxygen will then use the output that the filter program writes\n"
                  "to standard output.\n"
-                 "If FILTER_PATTERNS is specified, this tag will be\n"
-                 "ignored."
+                 "If FILTER_PATTERNS is specified, this tag will be ignored.\n"
+                 "Note that the filter must not add or remove lines; it is applied before the\n"
+                 "code is scanned, but not when the output code is generated.  If lines are\n"
+                 "added or removed, the anchors will not be placed correctly."
                 );
   cs->setWidgetType(ConfigString::File);
   //----