diff --git a/user_guide_src/source/general/common_functions.rst b/user_guide_src/source/general/common_functions.rst
index 66dabd9..7917d32 100644
--- a/user_guide_src/source/general/common_functions.rst
+++ b/user_guide_src/source/general/common_functions.rst
@@ -178,8 +178,8 @@
 Returns TRUE if a secure (HTTPS) connection is used and FALSE
 in any other case (including non-HTTP requests).
 
-function_usable($function_name)
-===============================
+function_usable()
+=================
 
 .. php:function:: function_usable($function_name)