diff --git a/.github/workflows/CI.yml b/.github/workflows/CI.yml
index 47bf6b3..10d2580 100644
--- a/.github/workflows/CI.yml
+++ b/.github/workflows/CI.yml
@@ -23,7 +23,7 @@ jobs:
       - name: Apply problem matcher
         uses: ./
         with:
-          build-directory: ""
+          build-directory: build/
       
       - name: Test problem matcher
         run: |
diff --git a/src/gcc_matcher.jsontemplate b/src/gcc_matcher.jsontemplate
index d157a38..9019aee 100644
--- a/src/gcc_matcher.jsontemplate
+++ b/src/gcc_matcher.jsontemplate
@@ -4,12 +4,13 @@
             "owner": "gcc-problem-matcher",
             "pattern": [
                 {
-                    "regexp": "^.*?${{ BASE }}\/?(.*?):(\\d+):(\\d*):?\\s+(?:fatal\\s+)?(warning|error):\\s+(.*)$",
-                    "file": 1,
-                    "line": 2,
-                    "column": 3,
-                    "severity": 4,
-                    "message": 5
+                    "regexp": "^(${{ BASE }})(.*?):(\\d+):(\\d*):?\\s+(?:fatal\\s+)?(warning|error):\\s+(.*)$",
+                    "fromPath": 1,
+                    "file": 2,
+                    "line": 3,
+                    "column": 4,
+                    "severity": 5,
+                    "message": 6
                 }
             ]
         }
diff --git a/src/index.js b/src/index.js
index 0a60ade..b58216e 100644
--- a/src/index.js
+++ b/src/index.js
@@ -21,7 +21,7 @@ const matcherPath = path.join(__dirname, "gcc_matcher.json");
 // rootdir :: string
 const rootdir = core.getInput('build-directory', {required: false});
 
-// parse :: IO() => IO() => Error | null
+// parse :: string => string => Error | null
 const parse = (templatePath) => (matcherPath) => {
 	const content = fs.readFileSync(templatePath, 'utf-8');