diff --git a/src/MyBinding.h b/src/MyBinding.h
index 72a8889..ecdd635 100644
--- a/src/MyBinding.h
+++ b/src/MyBinding.h
@@ -97,7 +97,7 @@ class MyBinding {
       }
       case MY_DATE:
       case MY_DATE_TIME:
-        if (isnan(REAL(col)[i])) {
+        if (ISNAN(REAL(col)[i])) {
           missing = true;
           break;
         } else {