diff --git a/crates/oxide_compiler/src/emitter.rs b/crates/oxide_compiler/src/emitter.rs
index d79047f..9af1e2a 100644
--- a/crates/oxide_compiler/src/emitter.rs
+++ b/crates/oxide_compiler/src/emitter.rs
@@ -908,7 +908,9 @@ impl Compiler {
                             AssignmentOperator::Division => OpCode::COMPOUND_MEMBER_DIV,
                             AssignmentOperator::Remainder => OpCode::COMPOUND_MEMBER_MOD,
                             AssignmentOperator::Exponential => OpCode::COMPOUND_MEMBER_EXP,
-                            _ => unreachable!(),
+                            _ => {
+                                return Err(format!("compound assignment operator {:?} not supported", assign.operator))
+                            }
                         };
                         ctx.emit(opcode::encode(op, obj_reg, val_reg, key_reg));
                         ctx.emit(0);
@@ -947,7 +949,12 @@ impl Compiler {
                                 AssignmentOperator::Division => OpCode::COMPOUND_DIV,
                                 AssignmentOperator::Remainder => OpCode::COMPOUND_MOD,
                                 AssignmentOperator::Exponential => OpCode::COMPOUND_EXP,
-                                _ => unreachable!(),
+                                _ => {
+                                    return Err(format!(
+                                        "compound assignment operator {:?} not supported",
+                                        assign.operator
+                                    ))
+                                }
                             };
                             ctx.emit(opcode::encode(op, var_reg, rhs, 0));
                             Ok(var_reg)
diff --git a/crates/oxide_compiler/tests/compile_expr_tests.rs b/crates/oxide_compiler/tests/compile_expr_tests.rs
index 838141f..44c6cfe 100644
--- a/crates/oxide_compiler/tests/compile_expr_tests.rs
+++ b/crates/oxide_compiler/tests/compile_expr_tests.rs
@@ -9,6 +9,16 @@ fn compile_source(source: &str) -> oxide_compiler::module::CompiledModule {
     compiler.compile(&program).expect("compile failed")
 }
 
+fn compile_source_err(source: &str) -> String {
+    let allocator = Allocator::default();
+    let program = oxide_parser::parse(&allocator, source).expect("parse failed");
+    let compiler = Compiler::new();
+    match compiler.compile(&program) {
+        Ok(_) => panic!("compile should fail"),
+        Err(err) => err,
+    }
+}
+
 #[test]
 fn compile_simple_expr() {
     let module = compile_source("1 + 2");
@@ -20,6 +30,20 @@ fn compile_simple_expr() {
     assert_eq!(last, OpCode::HALT);
 }
 
+#[test]
+fn unsupported_logical_assignment_returns_compile_error() {
+    let err = compile_source_err("let x = 0; x ||= 1;");
+    assert!(err.contains("compound assignment operator"));
+    assert!(err.contains("not supported"));
+}
+
+#[test]
+fn unsupported_member_logical_assignment_returns_compile_error() {
+    let err = compile_source_err("let obj = { x: 0 }; obj.x ||= 1;");
+    assert!(err.contains("compound assignment operator"));
+    assert!(err.contains("not supported"));
+}
+
 #[test]
 fn compile_constants() {
     let module = compile_source("42");