diff --git a/src/bun/ffi.ts b/src/bun/ffi.ts
index 95314b6..0e81fb8 100644
--- a/src/bun/ffi.ts
+++ b/src/bun/ffi.ts
@@ -37,12 +37,20 @@ try {
 }
 
 const { tcgetattr, tcsetattr, cfmakeraw } = cStdLib.symbols;
+let closed = false;
 const BunFFI: IFFI = {
 	tcgetattr,
 	tcsetattr,
 	cfmakeraw,
 	getPointer: ptr,
-	close: cStdLib.close,
+	close: () => {
+		if (!closed) {
+			cStdLib.close();
+			closed = true;
+		}
+
+		// Do nothing if FFI library was already closed
+	},
 };
 
 export default BunFFI;
diff --git a/src/common/termios.ts b/src/common/termios.ts
index e49cd0e..fc7f464 100644
--- a/src/common/termios.ts
+++ b/src/common/termios.ts
@@ -43,7 +43,7 @@ class Termios {
 	 * The pointer to the termios struct
 	 * @private
 	 */
-	#ptr: unknown;
+	readonly #ptr: unknown;
 
 	constructor(ffi: IFFI) {
 		this.#ffi = ffi;
diff --git a/src/deno/ffi.ts b/src/deno/ffi.ts
index e10530b..f9c2f32 100644
--- a/src/deno/ffi.ts
+++ b/src/deno/ffi.ts
@@ -1,20 +1,20 @@
 // Deno-specific ffi code
 import { IFFI } from '../common/runtime.ts';
 
-let libSuffix = '';
+let suffix = '';
 switch (Deno.build.os) {
 	case 'windows':
-		libSuffix = 'dll';
+		suffix = 'dll';
 		break;
 	case 'darwin':
-		libSuffix = 'dylib';
+		suffix = 'dylib';
 		break;
 	default:
-		libSuffix = 'so.6';
+		suffix = 'so.6';
 		break;
 }
 
-const cSharedLib = `libc.${libSuffix}`;
+const cSharedLib = `libc.${suffix}`;
 const cStdLib = Deno.dlopen(
 	cSharedLib,
 	{
@@ -41,8 +41,11 @@ const DenoFFI: IFFI = {
 	cfmakeraw,
 	getPointer: Deno.UnsafePointer.of,
 	close: () => {
-		if (closed === false) {
-			cStdLib.close();
+		if (!closed) {
+			// Closing appears to do bad things on macOS
+			if (Deno.build.os !== 'darwin') {
+				cStdLib.close();
+			}
 			closed = true;
 		}