diff --git a/src/libCom/calc/calcPerform.c b/src/libCom/calc/calcPerform.c
index 9984aae42..459c9fb2d 100644
--- a/src/libCom/calc/calcPerform.c
+++ b/src/libCom/calc/calcPerform.c
@@ -105,6 +105,7 @@
 #include	<stdio.h>
 #include	<string.h>
 #include	<math.h>
+#include	<epicsMath.h>
 
 #include	"dbDefs.h"
 
@@ -511,7 +512,7 @@ printf ("*FINISHED*\n");
 		*presult = *pstacktop;
 	else
 		return(-1);
-	return(0);
+	return((epicsIsNAN(*presult) ? -1 : 0));
 }