diff --git a/src/evaluator/expression/prefix/mod.rs b/src/evaluator/expression/prefix/mod.rs
index 869f61a2..e4916dc3 100644
--- a/src/evaluator/expression/prefix/mod.rs
+++ b/src/evaluator/expression/prefix/mod.rs
@@ -25,7 +25,7 @@ impl Evaluator {
 
         match object {
             Object::Integer { value } => Ok(Object::Integer { value: -value }),
-            _ => Err(EvaluationError::UnknownOperator),
+            _ => Err(EvaluationError::TypeMismatch),
         }
     }
 }
diff --git a/src/tests/evaluation_error/type_mismatch_boolean_prefix_expression/snapshots/monkey_interpreter__tests__evaluation_error__type_mismatch_boolean_prefix_expression__test_type_mismatch_boolean_prefix_expression_case_1_evaluation_error.snap b/src/tests/evaluation_error/type_mismatch_boolean_prefix_expression/snapshots/monkey_interpreter__tests__evaluation_error__type_mismatch_boolean_prefix_expression__test_type_mismatch_boolean_prefix_expression_case_1_evaluation_error.snap
index 778a5332..11f1e03c 100644
--- a/src/tests/evaluation_error/type_mismatch_boolean_prefix_expression/snapshots/monkey_interpreter__tests__evaluation_error__type_mismatch_boolean_prefix_expression__test_type_mismatch_boolean_prefix_expression_case_1_evaluation_error.snap
+++ b/src/tests/evaluation_error/type_mismatch_boolean_prefix_expression/snapshots/monkey_interpreter__tests__evaluation_error__type_mismatch_boolean_prefix_expression__test_type_mismatch_boolean_prefix_expression_case_1_evaluation_error.snap
@@ -3,5 +3,5 @@ source: src/tests/evaluation_error/type_mismatch_boolean_prefix_expression/mod.r
 expression: error
 ---
 Err(
-    UnknownOperator,
+    TypeMismatch,
 )
diff --git a/src/tests/evaluation_error/type_mismatch_boolean_prefix_expression/snapshots/monkey_interpreter__tests__evaluation_error__type_mismatch_boolean_prefix_expression__test_type_mismatch_boolean_prefix_expression_case_2_evaluation_error.snap b/src/tests/evaluation_error/type_mismatch_boolean_prefix_expression/snapshots/monkey_interpreter__tests__evaluation_error__type_mismatch_boolean_prefix_expression__test_type_mismatch_boolean_prefix_expression_case_2_evaluation_error.snap
index 778a5332..11f1e03c 100644
--- a/src/tests/evaluation_error/type_mismatch_boolean_prefix_expression/snapshots/monkey_interpreter__tests__evaluation_error__type_mismatch_boolean_prefix_expression__test_type_mismatch_boolean_prefix_expression_case_2_evaluation_error.snap
+++ b/src/tests/evaluation_error/type_mismatch_boolean_prefix_expression/snapshots/monkey_interpreter__tests__evaluation_error__type_mismatch_boolean_prefix_expression__test_type_mismatch_boolean_prefix_expression_case_2_evaluation_error.snap
@@ -3,5 +3,5 @@ source: src/tests/evaluation_error/type_mismatch_boolean_prefix_expression/mod.r
 expression: error
 ---
 Err(
-    UnknownOperator,
+    TypeMismatch,
 )
diff --git a/src/tests/evaluation_error/type_mismatch_boolean_prefix_expression/snapshots/monkey_interpreter__tests__evaluation_error__type_mismatch_boolean_prefix_expression__test_type_mismatch_boolean_prefix_expression_case_3_evaluation_error.snap b/src/tests/evaluation_error/type_mismatch_boolean_prefix_expression/snapshots/monkey_interpreter__tests__evaluation_error__type_mismatch_boolean_prefix_expression__test_type_mismatch_boolean_prefix_expression_case_3_evaluation_error.snap
index 778a5332..11f1e03c 100644
--- a/src/tests/evaluation_error/type_mismatch_boolean_prefix_expression/snapshots/monkey_interpreter__tests__evaluation_error__type_mismatch_boolean_prefix_expression__test_type_mismatch_boolean_prefix_expression_case_3_evaluation_error.snap
+++ b/src/tests/evaluation_error/type_mismatch_boolean_prefix_expression/snapshots/monkey_interpreter__tests__evaluation_error__type_mismatch_boolean_prefix_expression__test_type_mismatch_boolean_prefix_expression_case_3_evaluation_error.snap
@@ -3,5 +3,5 @@ source: src/tests/evaluation_error/type_mismatch_boolean_prefix_expression/mod.r
 expression: error
 ---
 Err(
-    UnknownOperator,
+    TypeMismatch,
 )
diff --git a/src/tests/evaluation_error/type_mismatch_boolean_prefix_expression/snapshots/monkey_interpreter__tests__evaluation_error__type_mismatch_boolean_prefix_expression__test_type_mismatch_boolean_prefix_expression_case_4_evaluation_error.snap b/src/tests/evaluation_error/type_mismatch_boolean_prefix_expression/snapshots/monkey_interpreter__tests__evaluation_error__type_mismatch_boolean_prefix_expression__test_type_mismatch_boolean_prefix_expression_case_4_evaluation_error.snap
index 778a5332..11f1e03c 100644
--- a/src/tests/evaluation_error/type_mismatch_boolean_prefix_expression/snapshots/monkey_interpreter__tests__evaluation_error__type_mismatch_boolean_prefix_expression__test_type_mismatch_boolean_prefix_expression_case_4_evaluation_error.snap
+++ b/src/tests/evaluation_error/type_mismatch_boolean_prefix_expression/snapshots/monkey_interpreter__tests__evaluation_error__type_mismatch_boolean_prefix_expression__test_type_mismatch_boolean_prefix_expression_case_4_evaluation_error.snap
@@ -3,5 +3,5 @@ source: src/tests/evaluation_error/type_mismatch_boolean_prefix_expression/mod.r
 expression: error
 ---
 Err(
-    UnknownOperator,
+    TypeMismatch,
 )