diff --git a/src/index.js b/src/index.js
index 480e2db..182157a 100644
--- a/src/index.js
+++ b/src/index.js
@@ -17,13 +17,20 @@ const inject = () => {
       return callback(new PluginError(PLUGIN_NAME, 'Streaming not supported'))
     }
 
-    const regex = /(?:<!--|\/\*)\s*?inject:\s*?([^\s].+?)\s*?(?:-->|\*\/)/gi
+    const regex = /[\t ]*(?:<!--|\/\*)\s*?inject:\s*?([^\s].+?)\s*?(?:-->|\*\/)/gi
 
-    const newFileContents = String(file.contents).replace(regex, (_, src) => {
+    const newFileContents = String(file.contents).replace(regex, (g0, src) => {
+      const prefix = g0.match(/^[\t ]*/)[0] || ''
       const sourcePath = src.startsWith('/')
         ? path.join(process.cwd(), src)
         : path.join(file.dirname, src)
-      return String(fs.readFileSync(sourcePath))
+      const content = String(fs.readFileSync(sourcePath))
+      return content
+        .split('\n')
+        .map(line =>
+          line && line.trim() ? prefix + line : line.endsWith('\r') ? '\r' : ''
+        )
+        .join('\n')
     })
 
     file.contents = Buffer.from(newFileContents)
diff --git a/test/fixtures/css/style.css b/test/fixtures/css/style.css
index 0fbbcd6..9cc7a64 100644
--- a/test/fixtures/css/style.css
+++ b/test/fixtures/css/style.css
@@ -1,21 +1,21 @@
 body {
-        width: 100vw;
-        height: 100vh;
+  width: 100vw;
+  height: 100vh;
 
-        margin: 0;
-        padding: 0;
+  margin: 0;
+  padding: 0;
 
-        display: flex;
-        align-items: center;
-        justify-content: center;
-        align-content: center;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  align-content: center;
 
-        background-color: #4a596b;
-      }
-      h1 {
-        width: 50%;
-        color: #eeeeee;
+  background-color: #4a596b;
+}
+h1 {
+  width: 50%;
+  color: #eeeeee;
 
-        text-align: center;
-        font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;
-      }
\ No newline at end of file
+  text-align: center;
+  font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;
+}
\ No newline at end of file
diff --git a/test/fixtures/template/head.html b/test/fixtures/template/head.html
index 060feae..7ef1906 100644
--- a/test/fixtures/template/head.html
+++ b/test/fixtures/template/head.html
@@ -1,3 +1,3 @@
 <meta charset="utf-8">
-    <meta name="viewport" content="width=device-width">
-    <meta title="test">
\ No newline at end of file
+<meta name="viewport" content="width=device-width">
+<meta title="test">
\ No newline at end of file