diff --git a/package.json b/package.json
index 887538b2..9c2a768c 100644
--- a/package.json
+++ b/package.json
@@ -95,7 +95,7 @@
     "rollup": "^2.0.0",
     "rollup-plugin-babel": "^4.3.3",
     "rollup-plugin-terser": "^5.2.0",
-    "sapper": "nolanlawson/sapper#for-pinafore-20",
+    "sapper": "nolanlawson/sapper#for-pinafore-21",
     "stringz": "^2.1.0",
     "svelte": "^2.16.1",
     "svelte-extras": "^2.0.2",
diff --git a/yarn.lock b/yarn.lock
index 926ea419..06e2e6cf 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -7594,9 +7594,9 @@ sanitize-filename@^1.6.0:
   dependencies:
     truncate-utf8-bytes "^1.0.0"
 
-sapper@nolanlawson/sapper#for-pinafore-20:
-  version "0.25.0"
-  resolved "https://codeload.github.com/nolanlawson/sapper/tar.gz/fb89e84a3b7b46e98c2043b5bfd7605dc3e59cde"
+sapper@nolanlawson/sapper#for-pinafore-21:
+  version "0.27.12"
+  resolved "https://codeload.github.com/nolanlawson/sapper/tar.gz/b1bfa42b124ef087958c2129b6b19e5f053e1884"
   dependencies:
     html-minifier "^3.5.20"
     http-link-header "^1.0.2"