diff --git a/cozo-core/src/data/functions.rs b/cozo-core/src/data/functions.rs
index aca38beb..5aa07a38 100644
--- a/cozo-core/src/data/functions.rs
+++ b/cozo-core/src/data/functions.rs
@@ -1069,6 +1069,9 @@ define_op!(OP_MOD, 2, false);
 pub(crate) fn op_mod(args: &[DataValue]) -> Result<DataValue> {
     Ok(match (&args[0], &args[1]) {
         (DataValue::Num(Num::Int(a)), DataValue::Num(Num::Int(b))) => {
+            if *b == 0 {
+                bail!("'mod' requires non-zero divisor")
+            }
             DataValue::Num(Num::Int(a.rem(b)))
         }
         (DataValue::Num(Num::Float(a)), DataValue::Num(Num::Float(b))) => {
diff --git a/cozo-core/src/data/tests/functions.rs b/cozo-core/src/data/tests/functions.rs
index 13a55f4b..1d0e5b13 100644
--- a/cozo-core/src/data/tests/functions.rs
+++ b/cozo-core/src/data/tests/functions.rs
@@ -80,6 +80,7 @@ fn test_div() {
         op_div(&[DataValue::from(7.0), DataValue::from(0.5)]).unwrap(),
         DataValue::from(14.0)
     );
+    assert!(op_div(&[DataValue::from(1), DataValue::from(0)]).is_ok());
 }
 
 #[test]
@@ -538,6 +539,10 @@ fn test_mod() {
         op_mod(&[DataValue::from(-10), DataValue::from(7)]).unwrap(),
         DataValue::from(-3)
     );
+    assert!(op_mod(&[DataValue::from(5), DataValue::from(0.)]).is_ok());
+    assert!(op_mod(&[DataValue::from(5.), DataValue::from(0.)]).is_ok());
+    assert!(op_mod(&[DataValue::from(5.), DataValue::from(0)]).is_ok());
+    assert!(op_mod(&[DataValue::from(5), DataValue::from(0)]).is_err());
 }
 
 #[test]
@@ -1476,4 +1481,4 @@ fn test_range() {
         .unwrap()
         .into_json();
     assert_eq!(res["rows"][0][0], json!([15, 13, 11, 9, 7, 5]));
-}
\ No newline at end of file
+}