diff --git a/packages/tailwindcss-language-server/src/project-locator.ts b/packages/tailwindcss-language-server/src/project-locator.ts
index 93f484cc..e102b279 100644
--- a/packages/tailwindcss-language-server/src/project-locator.ts
+++ b/packages/tailwindcss-language-server/src/project-locator.ts
@@ -16,6 +16,7 @@ import resolveFrom from './util/resolveFrom'
 import { type Feature, supportedFeatures } from '@tailwindcss/language-service/src/features'
 import { pathToFileURL } from 'node:url'
 import { resolveCssImports } from './resolve-css-imports'
+import { normalizeDriveLetter } from './utils'
 
 export interface ProjectConfig {
   /** The folder that contains the project */
@@ -70,6 +71,22 @@ export class ProjectLocator {
       })
     }
 
+    // Normalize drive letters in filepaths on Windows so paths
+    // are consistent across the filesystem and the language client
+    for (let project of projects) {
+      project.folder = normalizeDriveLetter(project.folder)
+      project.configPath = normalizeDriveLetter(project.configPath)
+      project.config.path = normalizeDriveLetter(project.config.path)
+
+      for (let entry of project.config.entries) {
+        entry.path = normalizeDriveLetter(entry.path)
+      }
+
+      for (let selector of project.documentSelector) {
+        selector.pattern = normalizeDriveLetter(selector.pattern)
+      }
+    }
+
     return projects
   }
 
diff --git a/packages/tailwindcss-language-server/src/tw.ts b/packages/tailwindcss-language-server/src/tw.ts
index 7fc82afb..0ec39309 100644
--- a/packages/tailwindcss-language-server/src/tw.ts
+++ b/packages/tailwindcss-language-server/src/tw.ts
@@ -282,6 +282,10 @@ export class TW {
 
       changeLoop: for (let change of changes) {
         let normalizedFilename = normalizePath(change.file)
+
+        // This filename comes from VSCode rather than from the filesystem
+        // which means the drive letter *might* be lowercased and we need
+        // to normalize it so that we can compare it properly.
         normalizedFilename = normalizeDriveLetter(normalizedFilename)
 
         for (let ignorePattern of ignore) {
@@ -322,8 +326,6 @@ export class TW {
             ...project.projectConfig.config.entries.map((entry) => entry.path),
           ]
 
-          reloadableFiles = reloadableFiles.map(normalizeDriveLetter)
-
           if (!changeAffectsFile(normalizedFilename, reloadableFiles)) continue
 
           needsSoftRestart = true
@@ -783,6 +785,12 @@ export class TW {
         for (let selector of documentSelector) {
           let fsPath = URI.parse(document.uri).fsPath
           let pattern = selector.pattern.replace(/[\[\]{}]/g, (m) => `\\${m}`)
+
+          // This filename comes from VSCode rather than from the filesystem
+          // which means the drive letter *might* be lowercased and we need
+          // to normalize it so that we can compare it properly.
+          fsPath = normalizeDriveLetter(fsPath)
+
           if (pattern.startsWith('!') && picomatch(pattern.slice(1), { dot: true })(fsPath)) {
             break
           }
diff --git a/packages/vscode-tailwindcss/CHANGELOG.md b/packages/vscode-tailwindcss/CHANGELOG.md
index c2591923..0764ef8b 100644
--- a/packages/vscode-tailwindcss/CHANGELOG.md
+++ b/packages/vscode-tailwindcss/CHANGELOG.md
@@ -2,7 +2,7 @@
 
 ## Prerelease
 
-- Nothing yet!
+- Normalize Windows drive letters in document URIs ([#980](https://github.com/tailwindlabs/tailwindcss-intellisense/pull/980))
 
 ## 0.12.0