diff --git a/src/font_file.rs b/src/font_file.rs
index b0bbd76..a3c420a 100644
--- a/src/font_file.rs
+++ b/src/font_file.rs
@@ -11,6 +11,7 @@ use std::ptr;
 use std::slice;
 use std::sync::Arc;
 use winapi::ctypes::c_void;
+use winapi::shared::winerror::S_OK;
 use winapi::um::dwrite::{IDWriteFontFace, IDWriteFontFile, IDWriteFontFileStream};
 use winapi::um::dwrite::{IDWriteFontFileLoader, IDWriteLocalFontFileLoader};
 use winapi::um::dwrite::{DWRITE_FONT_FACE_TYPE, DWRITE_FONT_FILE_TYPE_UNKNOWN};
@@ -147,68 +148,91 @@ impl FontFile {
         (*self.native.get()).clone()
     }
 
+    #[deprecated(note = "Use `font_file_bytes` instead.")]
+    pub fn get_font_file_bytes(&self) -> Vec<u8> {
+        self.font_file_bytes().unwrap()
+    }
+
     // This is a helper to read the contents of this FontFile,
     // without requiring callers to deal with loaders, keys,
     // or streams.
-    pub fn get_font_file_bytes(&self) -> Vec<u8> {
+    pub fn font_file_bytes(&self) -> Result<Vec<u8>, HRESULT> {
         unsafe {
             let mut ref_key: *const c_void = ptr::null();
             let mut ref_key_size: u32 = 0;
             let hr = (*self.native.get()).GetReferenceKey(&mut ref_key, &mut ref_key_size);
-            assert!(hr == 0);
+            if hr != S_OK {
+                return Err(hr);
+            }
 
             let mut loader: *mut IDWriteFontFileLoader = ptr::null_mut();
             let hr = (*self.native.get()).GetLoader(&mut loader);
-            assert!(hr == 0);
+            if hr != S_OK {
+                return Err(hr);
+            }
             let loader = ComPtr::from_raw(loader);
 
             let mut stream: *mut IDWriteFontFileStream = ptr::null_mut();
             let hr = loader.CreateStreamFromKey(ref_key, ref_key_size, &mut stream);
-            assert!(hr == 0);
+            if hr != S_OK {
+                return Err(hr);
+            }
             let stream = ComPtr::from_raw(stream);
 
             let mut file_size: u64 = 0;
             let hr = stream.GetFileSize(&mut file_size);
-            assert!(hr == 0);
+            if hr != S_OK {
+                return Err(hr);
+            }
 
             let mut fragment_start: *const c_void = ptr::null();
             let mut fragment_context: *mut c_void = ptr::null_mut();
             let hr =
                 stream.ReadFileFragment(&mut fragment_start, 0, file_size, &mut fragment_context);
-            assert!(hr == 0);
+            if hr != S_OK {
+                return Err(hr);
+            }
 
             let in_ptr = slice::from_raw_parts(fragment_start as *const u8, file_size as usize);
             let bytes = in_ptr.to_vec();
 
             stream.ReleaseFileFragment(fragment_context);
 
-            bytes
+            Ok(bytes)
         }
     }
 
+    #[deprecated(note = "Use `font_file_path` instead.")]
+    pub fn get_font_file_path(&self) -> Option<PathBuf> {
+        self.font_file_path().ok()
+    }
+
     // This is a helper to get the path of a font file,
     // without requiring callers to deal with loaders.
-    pub fn get_font_file_path(&self) -> Option<PathBuf> {
+    pub fn font_file_path(&self) -> Result<PathBuf, HRESULT> {
         unsafe {
             let mut ref_key: *const c_void = ptr::null();
             let mut ref_key_size: u32 = 0;
             let hr = (*self.native.get()).GetReferenceKey(&mut ref_key, &mut ref_key_size);
-            assert!(hr == 0);
+            if hr != S_OK {
+                return Err(hr);
+            }
 
             let mut loader: *mut IDWriteFontFileLoader = ptr::null_mut();
             let hr = (*self.native.get()).GetLoader(&mut loader);
-            assert!(hr == 0);
+            if hr != S_OK {
+                return Err(hr);
+            }
             let loader = ComPtr::from_raw(loader);
 
-            let local_loader: ComPtr<IDWriteLocalFontFileLoader> = match loader.cast() {
-                Ok(local_loader) => local_loader,
-                Err(_) => return None,
-            };
+            let local_loader: ComPtr<IDWriteLocalFontFileLoader> = loader.cast()?;
 
             let mut file_path_len = 0;
             let hr =
                 local_loader.GetFilePathLengthFromKey(ref_key, ref_key_size, &mut file_path_len);
-            assert_eq!(hr, 0);
+            if hr != S_OK {
+                return Err(hr);
+            }
 
             let mut file_path_buf = vec![0; file_path_len as usize + 1];
             let hr = local_loader.GetFilePathFromKey(
@@ -217,13 +241,15 @@ impl FontFile {
                 file_path_buf.as_mut_ptr(),
                 file_path_len + 1,
             );
-            assert_eq!(hr, 0);
+            if hr != S_OK {
+                return Err(hr);
+            }
 
             if let Some(&0) = file_path_buf.last() {
                 file_path_buf.pop();
             }
 
-            Some(PathBuf::from(OsString::from_wide(&file_path_buf)))
+            Ok(PathBuf::from(OsString::from_wide(&file_path_buf)))
         }
     }