diff --git a/src/fuzz/fuzz-calendarspec.c b/src/fuzz/fuzz-calendarspec.c
index 55d86134948..8f031503e95 100644
--- a/src/fuzz/fuzz-calendarspec.c
+++ b/src/fuzz/fuzz-calendarspec.c
@@ -14,7 +14,7 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
 
         str = memdup_suffix0(data, size);
 
-        if (calendar_spec_from_string(str, &cspec) > 0) {
+        if (calendar_spec_from_string(str, &cspec) >= 0) {
                 (void) calendar_spec_valid(cspec);
                 (void) calendar_spec_normalize(cspec);
                 (void) calendar_spec_to_string(cspec, &p);