diff --git a/src/compiler/moduleSpecifiers.ts b/src/compiler/moduleSpecifiers.ts
index ded50764ac..1155981541 100644
--- a/src/compiler/moduleSpecifiers.ts
+++ b/src/compiler/moduleSpecifiers.ts
@@ -9,7 +9,7 @@ namespace ts.moduleSpecifiers {
     export function getModuleSpecifier(
         compilerOptions: CompilerOptions,
         importingSourceFile: SourceFile,
-        importingSourceFileName: string,
+        importingSourceFileName: Path,
         toFileName: string,
         host: ModuleSpecifierResolutionHost,
         files: ReadonlyArray<SourceFile>,
@@ -48,10 +48,10 @@ namespace ts.moduleSpecifiers {
         readonly moduleResolutionKind: ModuleResolutionKind;
         readonly addJsExtension: boolean;
         readonly getCanonicalFileName: GetCanonicalFileName;
-        readonly sourceDirectory: string;
+        readonly sourceDirectory: Path;
     }
     // importingSourceFileName is separate because getEditsForFileRename may need to specify an updated path
-    function getInfo(compilerOptions: CompilerOptions, importingSourceFile: SourceFile, importingSourceFileName: string, host: ModuleSpecifierResolutionHost): Info {
+    function getInfo(compilerOptions: CompilerOptions, importingSourceFile: SourceFile, importingSourceFileName: Path, host: ModuleSpecifierResolutionHost): Info {
         const moduleResolutionKind = getEmitModuleResolutionKind(compilerOptions);
         const addJsExtension = usesJsExtensionOnImports(importingSourceFile);
         const getCanonicalFileName = createGetCanonicalFileName(host.useCaseSensitiveFileNames ? host.useCaseSensitiveFileNames() : true);
@@ -271,7 +271,7 @@ namespace ts.moduleSpecifiers {
         moduleFileName: string,
         host: ModuleSpecifierResolutionHost,
         getCanonicalFileName: (file: string) => string,
-        sourceDirectory: string,
+        sourceDirectory: Path,
     ): string | undefined {
         if (getEmitModuleResolutionKind(options) !== ModuleResolutionKind.NodeJs) {
             // nothing to do here
@@ -290,7 +290,7 @@ namespace ts.moduleSpecifiers {
         const moduleSpecifier = getDirectoryOrExtensionlessFileName(moduleFileName);
         // Get a path that's relative to node_modules or the importing file's path
         // if node_modules folder is in this folder or any of its parent folders, no need to keep it.
-        if (!startsWith(sourceDirectory, moduleSpecifier.substring(0, parts.topLevelNodeModulesIndex))) return undefined;
+        if (!startsWith(sourceDirectory, getCanonicalFileName(moduleSpecifier.substring(0, parts.topLevelNodeModulesIndex)))) return undefined;
         // If the module was found in @types, get the actual Node package name
         return getPackageNameFromAtTypesDirectory(moduleSpecifier.substring(parts.topLevelPackageNameIndex + 1));
 
diff --git a/src/harness/harnessLanguageService.ts b/src/harness/harnessLanguageService.ts
index e5dda42ff8..4376848e17 100644
--- a/src/harness/harnessLanguageService.ts
+++ b/src/harness/harnessLanguageService.ts
@@ -155,7 +155,7 @@ namespace Harness.LanguageService {
             this.vfs.mkdirpSync(ts.getDirectoryPath(newPath));
             this.vfs.renameSync(oldPath, newPath);
 
-            const updater = ts.getPathUpdater(oldPath, newPath, ts.createGetCanonicalFileName(/*useCaseSensitiveFileNames*/ false));
+            const updater = ts.getPathUpdater(oldPath, newPath, ts.createGetCanonicalFileName(this.useCaseSensitiveFileNames()));
             this.scriptInfos.forEach((scriptInfo, key) => {
                 const newFileName = updater(key);
                 if (newFileName !== undefined) {
@@ -189,6 +189,10 @@ namespace Harness.LanguageService {
             assert.isOk(script);
             return ts.computeLineAndCharacterOfPosition(script.getLineMap(), position);
         }
+
+        useCaseSensitiveFileNames() {
+            return !this.vfs.ignoreCase;
+        }
     }
 
     /// Native adapter
@@ -251,7 +255,6 @@ namespace Harness.LanguageService {
             return 0;
         }
 
-
         log = ts.noop;
         trace = ts.noop;
         error = ts.noop;
diff --git a/src/services/getEditsForFileRename.ts b/src/services/getEditsForFileRename.ts
index 43a0589536..bfb737ef03 100644
--- a/src/services/getEditsForFileRename.ts
+++ b/src/services/getEditsForFileRename.ts
@@ -104,8 +104,8 @@ namespace ts {
     ): void {
         const allFiles = program.getSourceFiles();
         for (const sourceFile of allFiles) {
-            const newFromOld = oldToNew(sourceFile.fileName);
-            const newImportFromPath = newFromOld !== undefined ? newFromOld : sourceFile.fileName;
+            const newFromOld = oldToNew(sourceFile.path) as Path;
+            const newImportFromPath = newFromOld !== undefined ? newFromOld : sourceFile.path;
             const newImportFromDirectory = getDirectoryPath(newImportFromPath);
 
             const oldFromNew: string | undefined = newToOld(sourceFile.fileName);
diff --git a/tests/baselines/reference/api/tsserverlibrary.d.ts b/tests/baselines/reference/api/tsserverlibrary.d.ts
index 28d019ed18..848e339432 100644
--- a/tests/baselines/reference/api/tsserverlibrary.d.ts
+++ b/tests/baselines/reference/api/tsserverlibrary.d.ts
@@ -9278,7 +9278,7 @@ declare namespace ts.moduleSpecifiers {
     interface ModuleSpecifierPreferences {
         readonly importModuleSpecifierPreference?: "relative" | "non-relative";
     }
-    function getModuleSpecifier(compilerOptions: CompilerOptions, importingSourceFile: SourceFile, importingSourceFileName: string, toFileName: string, host: ModuleSpecifierResolutionHost, files: ReadonlyArray<SourceFile>, preferences?: ModuleSpecifierPreferences): string;
+    function getModuleSpecifier(compilerOptions: CompilerOptions, importingSourceFile: SourceFile, importingSourceFileName: Path, toFileName: string, host: ModuleSpecifierResolutionHost, files: ReadonlyArray<SourceFile>, preferences?: ModuleSpecifierPreferences): string;
     function getModuleSpecifiers(moduleSymbol: Symbol, compilerOptions: CompilerOptions, importingSourceFile: SourceFile, host: ModuleSpecifierResolutionHost, files: ReadonlyArray<SourceFile>, preferences: ModuleSpecifierPreferences): ReadonlyArray<ReadonlyArray<string>>;
 }
 declare namespace ts {
diff --git a/tests/cases/fourslash/importNameCodeFix_getCanonicalFileName.ts b/tests/cases/fourslash/importNameCodeFix_getCanonicalFileName.ts
new file mode 100644
index 0000000000..73bcf7439a
--- /dev/null
+++ b/tests/cases/fourslash/importNameCodeFix_getCanonicalFileName.ts
@@ -0,0 +1,16 @@
+/// <reference path="fourslash.ts" />
+
+// @Filename: /howNow/node_modules/brownCow/index.d.ts
+////export const foo: number;
+
+// @Filename: /howNow/a.ts
+////foo;
+
+// Before fixing this bug, we compared a canonicalized `hownow` to a non-canonicalized `howNow`.
+
+goTo.file("/howNow/a.ts");
+verify.importFixAtPosition([
+`import { foo } from "brownCow";
+
+foo;`,
+]);