diff --git a/packages/openapi-generator/src/sourceFile.ts b/packages/openapi-generator/src/sourceFile.ts
index 3b375c16..9a6c78d5 100644
--- a/packages/openapi-generator/src/sourceFile.ts
+++ b/packages/openapi-generator/src/sourceFile.ts
@@ -19,18 +19,21 @@ export async function parseSource(
   src: string,
 ): Promise<SourceFile | undefined> {
   try {
-    const module = await swc.parse(src, {
+    // Parse an empty string to get the last span
+    const lastSpan = swc.parseSync('');
+
+    const module = swc.parseSync(src, {
       syntax: 'typescript',
       target: 'esnext',
+      comments: true,
     });
-    if (lastSpanEnd === -1) {
-      // Since the starting offset is seemingly arbitrary, simulate it by subtracting the length of the source file
-      // from the end of the first module. This probably doesn't matter since the first source file parsed will be
-      // the apiSpec file.
-      lastSpanEnd = module.span.end - src.length;
-    }
+
+    // Set the start of the module to the end of the last span, so that we don't have any
+    // issues when parsing files that start with comments
+    module.span.start = lastSpan.span.start;
+    lastSpanEnd = lastSpan.span.end;
+
     const symbols = parseTopLevelSymbols(src, lastSpanEnd, module.body);
-    lastSpanEnd = module.span.end;
     return {
       path,
       src,
diff --git a/packages/openapi-generator/test/codec.test.ts b/packages/openapi-generator/test/codec.test.ts
index b492e380..cf690994 100644
--- a/packages/openapi-generator/test/codec.test.ts
+++ b/packages/openapi-generator/test/codec.test.ts
@@ -638,8 +638,8 @@ testCase('first property comment is parsed', FIRST_PROPERTY_COMMENT, {
           problems: [],
           source: [
             {
-              number: 1,
-              source: '  /** this is a comment */',
+              number: 0,
+              source: '/** this is a comment */',
               tokens: {
                 delimiter: '/**',
                 description: 'this is a comment ',
@@ -650,7 +650,7 @@ testCase('first property comment is parsed', FIRST_PROPERTY_COMMENT, {
                 postName: '',
                 postTag: '',
                 postType: '',
-                start: '  ',
+                start: '',
                 tag: '',
                 type: '',
               },
@@ -685,8 +685,8 @@ testCase('second property comment is parsed', SECOND_PROPERTY_COMMENT, {
           problems: [],
           source: [
             {
-              number: 1,
-              source: '  /** this is a comment */',
+              number: 0,
+              source: '/** this is a comment */',
               tokens: {
                 delimiter: '/**',
                 description: 'this is a comment ',
@@ -697,7 +697,7 @@ testCase('second property comment is parsed', SECOND_PROPERTY_COMMENT, {
                 postName: '',
                 postTag: '',
                 postType: '',
-                start: '  ',
+                start: '',
                 tag: '',
                 type: '',
               },