diff --git a/hook/hr.c b/hook/hr.c
index 57eab7f..02a8642 100644
--- a/hook/hr.c
+++ b/hook/hr.c
@@ -4,29 +4,30 @@
 
 #include "hook/hr.h"
 
-void hr_propagate_win32_(HRESULT hr)
+uint32_t hr_to_win32_error(HRESULT hr)
 {
-    uint32_t result;
-
     if (SUCCEEDED(hr)) {
-        result = ERROR_SUCCESS;
+        return ERROR_SUCCESS;
     } else if (HRESULT_FACILITY(hr) == FACILITY_WIN32) {
-        result = HRESULT_CODE(hr);
+        return HRESULT_CODE(hr);
     } else {
         switch (hr) {
-        case E_ABORT:           result = ERROR_OPERATION_ABORTED; break;
-        case E_ACCESSDENIED:    result = ERROR_ACCESS_DENIED; break;
-        case E_FAIL:            result = ERROR_GEN_FAILURE; break;
-        case E_HANDLE:          result = ERROR_INVALID_HANDLE; break;
-        case E_INVALIDARG:      result = ERROR_INVALID_PARAMETER; break;
-        case E_NOINTERFACE:     result = ERROR_INVALID_FUNCTION; break;
-        case E_NOTIMPL:         result = ERROR_NOT_SUPPORTED; break;
-        case E_OUTOFMEMORY:     result = ERROR_OUTOFMEMORY; break;
-        case E_POINTER:         result = ERROR_INVALID_ADDRESS; break;
-        case E_UNEXPECTED:      result = ERROR_INTERNAL_ERROR; break;
-        default:                result = ERROR_INTERNAL_ERROR; break;
+        case E_ABORT:           return ERROR_OPERATION_ABORTED;
+        case E_ACCESSDENIED:    return ERROR_ACCESS_DENIED;
+        case E_FAIL:            return ERROR_GEN_FAILURE;
+        case E_HANDLE:          return ERROR_INVALID_HANDLE;
+        case E_INVALIDARG:      return ERROR_INVALID_PARAMETER;
+        case E_NOINTERFACE:     return ERROR_INVALID_FUNCTION;
+        case E_NOTIMPL:         return ERROR_NOT_SUPPORTED;
+        case E_OUTOFMEMORY:     return ERROR_OUTOFMEMORY;
+        case E_POINTER:         return ERROR_INVALID_ADDRESS;
+        case E_UNEXPECTED:      return ERROR_INTERNAL_ERROR;
+        default:                return ERROR_INTERNAL_ERROR;
         }
     }
+}
 
-    SetLastError(result);
+void hr_propagate_win32_(HRESULT hr)
+{
+    SetLastError(hr_to_win32_error(hr));
 }
diff --git a/hook/hr.h b/hook/hr.h
index 283d29b..29615cc 100644
--- a/hook/hr.h
+++ b/hook/hr.h
@@ -2,6 +2,9 @@
 
 #include <windows.h>
 
+#include <stdint.h>
+
 #define hr_propagate_win32(hr, r) (hr_propagate_win32_(hr), r)
 
+uint32_t hr_to_win32_error(HRESULT hr);
 void hr_propagate_win32_(HRESULT hr);