diff --git a/src/module.ts b/src/module.ts
index 317d9ef..af71143 100644
--- a/src/module.ts
+++ b/src/module.ts
@@ -26,13 +26,17 @@ export default defineNuxtModule<Partial<Options>>({
 
     nuxt.hook('vite:extendConfig', (config, { isClient }) => {
       const mode = isClient ? 'client' : 'server'
+      const sourcemapValue = nuxt.options.sourcemap[mode]
+      if (typeof sourcemapValue !== 'boolean') {
+        throw new TypeError(`Expected a boolean for sourcemap[${mode}], but received ${typeof sourcemapValue}.`)
+      }
 
       config.plugins = config.plugins || []
       config.plugins.push(
         transformPlugin.vite({
           include: options.include,
           exclude: options.exclude,
-          sourcemap: nuxt.options.sourcemap[mode] as boolean,
+          sourcemap: sourcemapValue,
           transformStyles: name => resolveStyles(options, name)
         })
       )
@@ -41,13 +45,17 @@ export default defineNuxtModule<Partial<Options>>({
     nuxt.hook('webpack:config', (configs) => {
       configs.forEach((config) => {
         const mode = config.name === 'client' ? 'client' : 'server'
+        const sourcemapValue = nuxt.options.sourcemap[mode]
+        if (typeof sourcemapValue !== 'boolean') {
+          throw new TypeError(`Expected a boolean for sourcemap[${mode}], but received ${typeof sourcemapValue}.`)
+        }
 
         config.plugins = config.plugins || []
         config.plugins.push(
           transformPlugin.webpack({
             include: options.include,
             exclude: options.exclude,
-            sourcemap: nuxt.options.sourcemap[mode] as boolean,
+            sourcemap: sourcemapValue,
             transformStyles: name => resolveStyles(options, name)
           })
         )