diff --git a/src/helpers.ts b/src/helpers.ts
index 2f26f8c..ae22037 100644
--- a/src/helpers.ts
+++ b/src/helpers.ts
@@ -1,3 +1,4 @@
+import { normalize } from "path";
 
 /**
  * Finds the matching suffixes of the string, stripping off the non-matching starting characters.
@@ -28,7 +29,9 @@ export function findIntersect(base: string, comparee: string): string {
  * @param fileName File name to remove OS specific features
  */
 export function normalizeFileName(fileName: string): string {
-    let name = fileName;
+    // properly handle relative file path bits
+    // See #351 https://github.com/ryanluker/vscode-coverage-gutters/issues/351
+    let name = normalize(fileName);
     // make file path relative and OS independent
     name = name.toLocaleLowerCase();
     // remove all file slashes
diff --git a/test/helpers.test.ts b/test/helpers.test.ts
index 92914b8..3773245 100644
--- a/test/helpers.test.ts
+++ b/test/helpers.test.ts
@@ -18,6 +18,10 @@ suite("helper Tests", function() {
             {fileName: "a/A/", expected: "a###a###"},
             {fileName: "/###/", expected: "#########"},
             {fileName: "\\/", expected: "######"},
+            {
+                expected: "###home###lt###projects###libfuzz###json-c###arraylist.c",
+                fileName: "/home/lt/projects/libfuzz/json-c/build/../arraylist.c",
+            },
         ].forEach((parameters) => {
             expect(normalizeFileName(parameters.fileName)).to.equal(parameters.expected);
         });