diff --git a/yamlreaders/__init__.py b/yamlreaders/__init__.py
index 9904c2b..48e2afc 100644
--- a/yamlreaders/__init__.py
+++ b/yamlreaders/__init__.py
@@ -6,6 +6,7 @@ from .openapi_reader import OpenAPIReader
 
 def get_reader(source: str) -> BaseReader:
     from pathlib import Path
+    import yaml
 
     path = Path(source)
 
@@ -13,12 +14,22 @@ def get_reader(source: str) -> BaseReader:
         raise FileNotFoundError(f"File not found: {path}")
 
     with open(path, "r", encoding="utf-8") as f:
-        first_line = f.readline().strip()
+        content = f.read(2048)
 
-    if '"openapi"' in first_line or "openapi:" in first_line:
-        return OpenAPIReader()
+    if "openapi:" in content:
+        try:
+            data = yaml.safe_load(content)
+            if isinstance(data, dict) and "openapi" in data:
+                return OpenAPIReader()
+        except Exception:
+            pass
 
-    if '"info"' in first_line and '"item"' in first_line:
-        return PostmanReader()
+    try:
+        data = yaml.safe_load(content)
+        if isinstance(data, dict):
+            if "info" in data and "item" in data:
+                return PostmanReader()
+    except Exception:
+        pass
 
     return YamlReader()