diff --git a/lib/isc/include/isc/result.h b/lib/isc/include/isc/result.h
index a2a21ce981..872aee3f35 100644
--- a/lib/isc/include/isc/result.h
+++ b/lib/isc/include/isc/result.h
@@ -41,7 +41,9 @@ typedef unsigned int isc_result_t;
 #define ISC_R_EXISTS			18
 #define ISC_R_TOOSMALL			19	/* buffer is too small */
 #define ISC_R_CANCELED			20
-#define ISC_R_LASTENTRY			20	/* last entry in the list */
+#define ISC_R_TASKNOSEND		21
+#define ISC_R_TASKSHUTTINGDOWN		22	/* task is shutting down */
+#define ISC_R_LASTENTRY			22	/* last entry in the list */
 
 #define ISC_R_UNEXPECTED		0xFFFFFFFFL
 
diff --git a/lib/isc/result.c b/lib/isc/result.c
index 2ba0e2d8c3..c3d0f50f8b 100644
--- a/lib/isc/result.c
+++ b/lib/isc/result.c
@@ -41,6 +41,8 @@ static char *text_table[ISC_R_LASTENTRY + 1] = {
 	"already exists",			/* 18 */
 	"buffer too small",			/* 19 */
 	"operation canceled",			/* 20 */
+	"sending events is not allowed",	/* 21 */
+	"task is shutting down",		/* 22 */
 };
 
 char *