diff --git a/news/6021.bugfix.rst b/news/6021.bugfix.rst
new file mode 100644
index 00000000..c3c82ca5
--- /dev/null
+++ b/news/6021.bugfix.rst
@@ -0,0 +1 @@
+Fix KeyError when using a source without a name in Pipfile
diff --git a/pipenv/project.py b/pipenv/project.py
index 9495370e..f06ef93c 100644
--- a/pipenv/project.py
+++ b/pipenv/project.py
@@ -1023,7 +1023,7 @@ class Project:
         return sources
 
     def get_default_index(self):
-        return self.pipfile_sources()[0]
+        return self.populate_source(self.pipfile_sources()[0])
 
     def get_index_by_name(self, index_name):
         for source in self.pipfile_sources():