diff --git a/demo/demo.ts b/demo/demo.ts
index 6f9e25f..485c054 100644
--- a/demo/demo.ts
+++ b/demo/demo.ts
@@ -50,7 +50,6 @@ async function launchCustomRom() {
   nostalgist = await Nostalgist.launch({
     core: 'fceumm',
     rom: await showOpenFilePicker().then(([fileHandle]) => fileHandle.getFile()),
-    shader: 'crt/crt-easymode',
   })
 }
 
diff --git a/src/nostalgist.ts b/src/nostalgist.ts
index 60116f9..0dc3511 100644
--- a/src/nostalgist.ts
+++ b/src/nostalgist.ts
@@ -30,9 +30,8 @@ export class Nostalgist {
   private emulator: Emulator | undefined
 
   private constructor(options: NostalgistLaunchOptions) {
-    const mergedOptions = {}
+    const mergedOptions = { ...Nostalgist.globalOptions, ...options }
     merge(mergedOptions, Nostalgist.globalOptions, options)
-    // @ts-expect-error we cannot infer the final type here
     this.options = mergedOptions
   }
 
@@ -602,13 +601,13 @@ export class Nostalgist {
   }
 
   private getRetroarchOption() {
-    const options = {}
+    const options = { ...Nostalgist.globalOptions.retroarchConfig, ...this.options.retroarchConfig }
     merge(options, Nostalgist.globalOptions.retroarchConfig, this.options.retroarchConfig)
     return options as typeof this.options.retroarchConfig
   }
 
   private getRetroarchCoreOption() {
-    const options = {}
+    const options = { ...Nostalgist.globalOptions.retroarchCoreConfig, ...this.options.retroarchCoreConfig }
     merge(options, Nostalgist.globalOptions.retroarchCoreConfig, this.options.retroarchCoreConfig)
     return options
   }