diff --git a/src/R_timestamp.c b/src/R_timestamp.c
index d5f22ab..9f79ddc 100644
--- a/src/R_timestamp.c
+++ b/src/R_timestamp.c
@@ -89,7 +89,11 @@ SEXP R_TimestampExt(int64_t ts)
 
 int64_t R_TimestampUnix(SEXP r_ts)
 {
-  return (int64_t)(Rf_asReal(VECTOR_ELT(r_ts, 0)) / 1);
+  if (TYPEOF(r_ts) == REALSXP) {
+    return (int64_t)(Rf_asReal(r_ts) / 1);
+  } else {
+    return (int64_t)(Rf_asReal(VECTOR_ELT(r_ts, 0)) / 1);
+  }
 }
 
 int64_t R_TimestampExtUnix(SEXP r_ts)