diff --git a/changelog/unreleased/fix-proofkeys-proxy.md b/changelog/unreleased/fix-proofkeys-proxy.md
new file mode 100644
index 000000000..1d04e9e10
--- /dev/null
+++ b/changelog/unreleased/fix-proofkeys-proxy.md
@@ -0,0 +1,5 @@
+Bugfix: Respect proxy url when validating proofkeys
+
+We fixed a bug where the proxied wopi URL was not used when validating proofkeys. This caused the validation to fail when the proxy was used.
+
+https://github.com/owncloud/ocis/pull/1234
diff --git a/services/collaboration/pkg/middleware/proofkeys.go b/services/collaboration/pkg/middleware/proofkeys.go
index c3b96835e..d3efc1e9b 100644
--- a/services/collaboration/pkg/middleware/proofkeys.go
+++ b/services/collaboration/pkg/middleware/proofkeys.go
@@ -35,6 +35,9 @@ func ProofKeysMiddleware(cfg *config.Config, next http.Handler) http.Handler {
 		// the url we need is the one being requested, but we need the
 		// scheme and host, so we'll get those from the configured WOPISrc
 		wopiSrcURL, _ := url.Parse(cfg.Wopi.WopiSrc)
+		if cfg.Wopi.ProxyURL != "" {
+			wopiSrcURL, _ = url.Parse(cfg.Wopi.ProxyURL)
+		}
 		currentURL, _ := url.Parse(r.URL.String())
 		currentURL.Scheme = wopiSrcURL.Scheme
 		currentURL.Host = wopiSrcURL.Host