diff --git a/docs/api.md b/docs/api.md
index 57e8689..947c7f0 100644
--- a/docs/api.md
+++ b/docs/api.md
@@ -97,7 +97,7 @@ Read and write vault files.
 - `const dataurl = await $.io.load_data_url( path, mimetype? )`
 	- Encode the contents of a file into a dataurl for use in a template
 	- Optionaly specify the mime type.
-	- Auto mime type mappings are available for the following file extensions: `.jpg`, `.png`, `.gif`, `.svg`, `.css`
+	- Auto mime type mappings are available for the following common file extensions: `.jpeg`, `.jpg`, `.png`, `.gif`, `.svg`, `.css`
 - `await $.io.output( file, content, open? )`
 	- (Over)Writes the `file` with given `content`
 	- Tries to open the `file` if `open` is true (false by default)
diff --git a/src/constants.ts b/src/constants.ts
index 5bb20dd..451103d 100644
--- a/src/constants.ts
+++ b/src/constants.ts
@@ -1,2 +1,12 @@
 export const CODE_BLOCK_LANG_TOOLBAR = 'meld-build-toolbar';
-export const URL_HELP = 'https://github.com/meld-cp/obsidian-build/blob/master/docs/user-guide.md';
\ No newline at end of file
+
+export const URL_HELP = 'https://github.com/meld-cp/obsidian-build/blob/master/docs/user-guide.md';
+
+export const EXTENSION_MIMETYPE_MAP = new  Map<string,string>([
+	['jpeg', 'image/jpeg'],
+	['jpg',	'image/jpeg'],
+	['png', 'image/png'],
+	['gif', 'image/gif'],
+	['svg', 'image/svg+xml'],
+	['css', 'text/css'],
+]);
diff --git a/src/rci-io.ts b/src/rci-io.ts
index e3ae38f..8cefc00 100644
--- a/src/rci-io.ts
+++ b/src/rci-io.ts
@@ -1,4 +1,5 @@
 import { normalizePath, TFile } from "obsidian";
+import { EXTENSION_MIMETYPE_MAP } from "./constants";
 import { DataSet, IDataSetCollection } from "./data-set";
 import { NamedCodeBlock } from "./named-code-block";
 import { Parser } from "./parser";
@@ -103,13 +104,10 @@ export class IoRunContextImplemention implements TIoRunContext {
 			return Promise.resolve(undefined);
 		}
 
-		const finalMimeType = mimetype ?? {
-			'jpg':'image/jpeg',
-			'png':'image/png',
-			'gif':'image/gif',
-			'svg':'image/svg+xml',
-			'css':'text/css'
-		}[af.extension] ?? '';
+		const finalMimeType = mimetype
+			?? EXTENSION_MIMETYPE_MAP.get(af.extension)
+			?? ''
+		;
 
 		const base64Data = Utils.toBase64( await app.vault.readBinary(af) );