diff --git a/src/dataurl.ts b/src/dataurl.ts
index 13bc8b43..092f61b1 100644
--- a/src/dataurl.ts
+++ b/src/dataurl.ts
@@ -37,7 +37,7 @@ export async function fetchAsDataURL<T>(
   })
 }
 
-const cache: { [url: string]: string } = {}
+const cache: { [url: string]: Promise<string> } = {}
 
 function getCacheKey(
   url: string,
@@ -58,27 +58,11 @@ function getCacheKey(
   return contentType ? `[${contentType}]${key}` : key
 }
 
-export async function resourceToDataURL(
+async function fetchAndMakeDataURL(
   resourceUrl: string,
   contentType: string | undefined,
   options: Options,
 ) {
-  const cacheKey = getCacheKey(
-    resourceUrl,
-    contentType,
-    options.includeQueryParams,
-  )
-
-  if (cache[cacheKey] != null) {
-    return cache[cacheKey]
-  }
-
-  // ref: https://developer.mozilla.org/en/docs/Web/API/XMLHttpRequest/Using_XMLHttpRequest#Bypassing_the_cache
-  if (options.cacheBust) {
-    // eslint-disable-next-line no-param-reassign
-    resourceUrl += (/\?/.test(resourceUrl) ? '&' : '?') + new Date().getTime()
-  }
-
   let dataURL: string
   try {
     const content = await fetchAsDataURL(
@@ -93,6 +77,7 @@ export async function resourceToDataURL(
       },
     )
     dataURL = makeDataUrl(content, contentType!)
+    return dataURL
   } catch (error) {
     dataURL = options.imagePlaceholder || ''
 
@@ -104,8 +89,31 @@ export async function resourceToDataURL(
     if (msg) {
       console.warn(msg)
     }
+    return dataURL
+  }
+}
+
+export async function resourceToDataURL(
+  resourceUrl: string,
+  contentType: string | undefined,
+  options: Options,
+) {
+  const cacheKey = getCacheKey(
+    resourceUrl,
+    contentType,
+    options.includeQueryParams,
+  )
+
+  if (cache[cacheKey] != null) {
+    return cache[cacheKey]
+  }
+
+  // ref: https://developer.mozilla.org/en/docs/Web/API/XMLHttpRequest/Using_XMLHttpRequest#Bypassing_the_cache
+  if (options.cacheBust) {
+    // eslint-disable-next-line no-param-reassign
+    resourceUrl += (/\?/.test(resourceUrl) ? '&' : '?') + new Date().getTime()
   }
 
-  cache[cacheKey] = dataURL
-  return dataURL
+  cache[cacheKey] = fetchAndMakeDataURL(resourceUrl, contentType, options)
+  return cache[cacheKey]
 }