diff --git a/internal/pkg/bifs/types.go b/internal/pkg/bifs/types.go
index 54fe8d3a0..59cb9c178 100644
--- a/internal/pkg/bifs/types.go
+++ b/internal/pkg/bifs/types.go
@@ -194,10 +194,10 @@ func BIF_is_notarray(input1 *mlrval.Mlrval) *mlrval.Mlrval {
 	return mlrval.FromBool(!input1.IsArray())
 }
 func BIF_is_notnull(input1 *mlrval.Mlrval) *mlrval.Mlrval {
-	return mlrval.FromBool(!input1.IsAbsent() && !input1.IsVoid())
+	return mlrval.FromBool(!input1.IsAbsent() && !input1.IsVoid() && !input1.IsNull())
 }
 func BIF_is_null(input1 *mlrval.Mlrval) *mlrval.Mlrval {
-	return mlrval.FromBool(input1.IsAbsent() || input1.IsVoid())
+	return mlrval.FromBool(input1.IsAbsent() || input1.IsVoid() || input1.IsNull())
 }
 func BIF_is_numeric(input1 *mlrval.Mlrval) *mlrval.Mlrval {
 	return mlrval.FromBool(input1.IsInt() || input1.IsFloat())
diff --git a/internal/pkg/dsl/cst/builtin_function_manager.go b/internal/pkg/dsl/cst/builtin_function_manager.go
index ce8849a8e..2b37c0286 100644
--- a/internal/pkg/dsl/cst/builtin_function_manager.go
+++ b/internal/pkg/dsl/cst/builtin_function_manager.go
@@ -1203,14 +1203,14 @@ strftime_local.`,
 		{
 			name:      "is_not_null",
 			class:     FUNC_CLASS_TYPING,
-			help:      "False if argument is null (empty or absent), true otherwise.",
+			help:      "False if argument is null (empty, absent, or JSON null), true otherwise.",
 			unaryFunc: bifs.BIF_is_notnull,
 		},
 
 		{
 			name:      "is_null",
 			class:     FUNC_CLASS_TYPING,
-			help:      "True if argument is null (empty or absent), false otherwise.",
+			help:      "True if argument is null (empty, absent, or JSON null), false otherwise.",
 			unaryFunc: bifs.BIF_is_null,
 		},