diff --git a/expect/linux-tpm.exp b/expect/linux-tpm.exp
index 6783503..8aff8ce 100644
--- a/expect/linux-tpm.exp
+++ b/expect/linux-tpm.exp
@@ -88,19 +88,14 @@
         }
 }
 
+expect_string "#" "finished reading PCRs"
+
 # Match the previously stored digest with the one generated by the
 # fTPM service. The pass criteria is that both digests must match,
 # meaning that TF-A successfully passed the event log to the TPM service.
-expect {
-        "#" {
-                spawn diff -s $TFA_DIGEST ftpm_event_log
-        }
+if {[catch {exec diff -s $TFA_DIGEST ftpm_event_log} result options] == 0} {
+        message "tests succeeded, digests matched"
+} else {
+        message "tests failed, digests did not match"
+        exit_uart -1
 }
-
-expect {
-        -exact "are identical" {
-                exit_uart 0
-        }
-}
-
-exit_uart -1