diff --git a/Structure-of-the-code.md b/Structure-of-the-code.md
index bbc08f0..624da9d 100644
--- a/Structure-of-the-code.md
+++ b/Structure-of-the-code.md
@@ -10,7 +10,7 @@ osxphotos is built around a set of classes that each handle a particular aspect
 
 The package code is organized in osxphotos per the table below. Most of the files contain doc strings describing what they contain. 
 
-## source files
+## Source files
 |file|description|
 |---|---|
 |`__init__.py`|              this is what gets read by "import osxphotos"|