diff --git a/Makefile b/Makefile
index 1ce69a3302..8e0461311e 100644
--- a/Makefile
+++ b/Makefile
@@ -7,13 +7,7 @@ build0:
 	CGO_ENABLED=0 go build
 	CGO_ENABLED=0 go vet ./...
 	./gendoc.sh
-	# we rewrite some dmarcprt and tlsrpt enums into untyped strings: real-world
-	# reports have invalid values, and our loose Go typed strings accept all values,
-	# but we don't want the typescript runtime checker to fail on those unrecognized
-	# values.
-	(cd webadmin && CGO_ENABLED=0 go run ../vendor/github.com/mjl-/sherpadoc/cmd/sherpadoc/*.go -adjust-function-names none -rename 'config Domain ConfigDomain,dmarc Policy DMARCPolicy,mtasts MX STSMX,tlsrptdb Record TLSReportRecord,tlsrptdb SuppressAddress TLSRPTSuppressAddress,dmarcrpt DKIMResult string,dmarcrpt SPFResult string,dmarcrpt SPFDomainScope string,dmarcrpt DMARCResult string,dmarcrpt PolicyOverride string,dmarcrpt Alignment string,dmarcrpt Disposition string,tlsrpt PolicyType string,tlsrpt ResultType string' Admin) >webadmin/api.json
-	(cd webaccount && CGO_ENABLED=0 go run ../vendor/github.com/mjl-/sherpadoc/cmd/sherpadoc/*.go -adjust-function-names none Account) >webaccount/api.json
-	(cd webmail && CGO_ENABLED=0 go run ../vendor/github.com/mjl-/sherpadoc/cmd/sherpadoc/*.go -adjust-function-names none Webmail) >webmail/api.json
+	./genapidoc.sh
 	./gents.sh webadmin/api.json webadmin/api.ts
 	./gents.sh webaccount/api.json webaccount/api.ts
 	./gents.sh webmail/api.json webmail/api.ts
diff --git a/genapidoc.sh b/genapidoc.sh
new file mode 100755
index 0000000000..548efe3936
--- /dev/null
+++ b/genapidoc.sh
@@ -0,0 +1,10 @@
+#!/bin/sh
+set -eu
+
+# we rewrite some dmarcprt and tlsrpt enums into untyped strings: real-world
+# reports have invalid values, and our loose Go typed strings accept all values,
+# but we don't want the typescript runtime checker to fail on those unrecognized
+# values.
+(cd webadmin && CGO_ENABLED=0 go run ../vendor/github.com/mjl-/sherpadoc/cmd/sherpadoc/*.go -adjust-function-names none -rename 'config Domain ConfigDomain,dmarc Policy DMARCPolicy,mtasts MX STSMX,tlsrptdb Record TLSReportRecord,tlsrptdb SuppressAddress TLSRPTSuppressAddress,dmarcrpt DKIMResult string,dmarcrpt SPFResult string,dmarcrpt SPFDomainScope string,dmarcrpt DMARCResult string,dmarcrpt PolicyOverride string,dmarcrpt Alignment string,dmarcrpt Disposition string,tlsrpt PolicyType string,tlsrpt ResultType string' Admin) >webadmin/api.json
+(cd webaccount && CGO_ENABLED=0 go run ../vendor/github.com/mjl-/sherpadoc/cmd/sherpadoc/*.go -adjust-function-names none Account) >webaccount/api.json
+(cd webmail && CGO_ENABLED=0 go run ../vendor/github.com/mjl-/sherpadoc/cmd/sherpadoc/*.go -adjust-function-names none Webmail) >webmail/api.json