diff --git a/src/command.ts b/src/command.ts
index 5160f30..7ac17d1 100644
--- a/src/command.ts
+++ b/src/command.ts
@@ -1075,7 +1075,7 @@ function validateCommandName(command: string) {
 const SHELL_SIGNAL_CTOR_SYMBOL = Symbol();
 
 interface KillSignalState {
-  abortedCode: number;
+  abortedCode: number | undefined;
   listeners: ((signal: Deno.Signal) => void)[];
 }
 
@@ -1086,7 +1086,7 @@ export class KillSignalController {
 
   constructor() {
     this.#state = {
-      abortedCode: 0,
+      abortedCode: undefined,
       listeners: [],
     };
     this.#killSignal = new KillSignal(SHELL_SIGNAL_CTOR_SYMBOL, this.#state);
@@ -1131,7 +1131,12 @@ export class KillSignal {
    * SIGKILL, SIGABRT, SIGQUIT, SIGINT, or SIGSTOP
    */
   get aborted(): boolean {
-    return this.#state.abortedCode !== 0;
+    return this.#state.abortedCode !== undefined;
+  }
+
+  /** Gets the exit code to use if aborted. */
+  get abortedExitCode(): number | undefined {
+    return this.#state.abortedCode;
   }
 
   /**
@@ -1160,11 +1165,6 @@ export class KillSignal {
       this.#state.listeners.splice(index, 1);
     }
   }
-
-  /** @internal - DO NOT USE. Very unstable. Not sure about this. */
-  get _abortedExitCode() {
-    return this.#state.abortedCode;
-  }
 }
 
 function sendSignalToState(state: KillSignalState, signal: Deno.Signal) {
diff --git a/src/commands/cat.ts b/src/commands/cat.ts
index 93392e4..51239dc 100644
--- a/src/commands/cat.ts
+++ b/src/commands/cat.ts
@@ -32,7 +32,7 @@ async function executeCat(context: CommandContext) {
           if (!size || size === 0) break;
           else context.stdout.writeSync(buf.slice(0, size));
         }
-        exitCode = context.signal._abortedExitCode;
+        exitCode = context.signal.abortedExitCode ?? 0;
       } else {
         const _assertValue: "null" | "inherit" = context.stdin;
         throw new Error(`not supported. stdin was '${context.stdin}'`);
@@ -47,7 +47,7 @@ async function executeCat(context: CommandContext) {
           if (!size || size === 0) break;
           else context.stdout.writeSync(buf.slice(0, size));
         }
-        exitCode = context.signal._abortedExitCode;
+        exitCode = context.signal.abortedExitCode ?? 0;
       } catch (err) {
         context.stderr.writeLine(`cat ${path}: ${err}`);
         exitCode = 1;