Rendering mermaid C4 diagrams - parse error

**Describe the bug**
C4 Diagram fails to render. Shows parse error

**To Reproduce**
Steps to reproduce the behavior:
1. Go to https://mermaid-js.github.io/mermaid/#/c4c
2. Grab sample syntax for C4 context diagram
3. Paste into a vimwiki file (surrounded by appropriate ```mermaid .... ``` )
4. See error.
`
Parse error on line 1:
C4Context ti
^
Expecting 'open_directive', 'NEWLINE', 'SPACE', 'GRAPH', got 'ALPHA'
`

**Expected behavior**
Other diagram types render correctly.
Same syntax renders correctly with mermaid-cli

**Desktop (please complete the following information):**
- OS: Linux Mint