--- a/crates/jsonnet-evaluator/src/error.rs
+++ b/crates/jsonnet-evaluator/src/error.rs
@@ -1,5 +1,5 @@
 use crate::ValType;
-use jsonnet_parser::ExprLocation;
+use jsonnet_parser::{BinaryOpType, ExprLocation, UnaryOpType};
 use std::{path::PathBuf, rc::Rc};
 
 #[derive(Debug, Clone)]
@@ -7,6 +7,9 @@
 	IntristicNotFound(Rc<str>, Rc<str>),
 	IntristicArgumentReorderingIsNotSupportedYet,
 
+	UnaryOperatorDoesNotOperateOnType(UnaryOpType, ValType),
+	BinaryOperatorDoesNotOperateOnValues(BinaryOpType, ValType, ValType),
+
 	VariableIsNotDefined(String),
 	TypeMismatch(&'static str, Vec<ValType>, ValType),
 	NoSuchField(Rc<str>),
--- a/crates/jsonnet-evaluator/src/evaluate.rs
+++ b/crates/jsonnet-evaluator/src/evaluate.rs
@@ -74,7 +74,10 @@
 		(UnaryOpType::Not, Val::Bool(v)) => Val::Bool(!v),
 		(UnaryOpType::Minus, Val::Num(n)) => Val::Num(-*n),
 		(UnaryOpType::BitNot, Val::Num(n)) => Val::Num(!(*n as i32) as f64),
-		(op, o) => panic!("unary op not implemented: {:?} {:?}", op, o),
+		(op, o) => create_error(Error::UnaryOperatorDoesNotOperateOnType(
+			op,
+			o.value_type()?,
+		))?,
 	})
 }
 
@@ -92,7 +95,11 @@
 		(Val::Obj(v1), Val::Obj(v2)) => Val::Obj(v2.with_super(v1.clone())),
 		(Val::Arr(a), Val::Arr(b)) => Val::Arr(Rc::new([&a[..], &b[..]].concat())),
 		(Val::Num(v1), Val::Num(v2)) => Val::Num(v1 + v2),
-		_ => panic!("can't add: {:?} and {:?}", a, b),
+		_ => create_error(Error::BinaryOperatorDoesNotOperateOnValues(
+			BinaryOpType::Add,
+			a.value_type()?,
+			b.value_type()?,
+		))?,
 	})
 }
 
@@ -161,7 +168,11 @@
 			Val::Num(((*v1 as i32) >> (*v2 as i32)) as f64)
 		}
 
-		_ => panic!("no rules for binary operation: {:?} {:?} {:?}", a, op, b),
+		_ => create_error(Error::BinaryOperatorDoesNotOperateOnValues(
+			op,
+			a.value_type()?,
+			b.value_type()?,
+		))?,
 	})
 }