diff --git a/src/rust-crypto/verification.ts b/src/rust-crypto/verification.ts
index 424945cb7..d25e6b26d 100644
--- a/src/rust-crypto/verification.ts
+++ b/src/rust-crypto/verification.ts
@@ -710,10 +710,16 @@ export class RustSASVerifier extends BaseRustVerifer<RustSdkCryptoJs.Sas> implem
                     }
                 },
                 mismatch: (): void => {
-                    throw new Error("impl");
+                    const request = this.inner.cancelWithCode("m.mismatched_sas");
+                    if (request) {
+                        this.outgoingRequestProcessor.makeOutgoingRequest(request);
+                    }
                 },
                 cancel: (): void => {
-                    throw new Error("impl");
+                    const request = this.inner.cancelWithCode("m.user");
+                    if (request) {
+                        this.outgoingRequestProcessor.makeOutgoingRequest(request);
+                    }
                 },
             };
             this.emit(VerifierEvent.ShowSas, this.callbacks);