diff --git a/src/windows/WinMiniFB.c b/src/windows/WinMiniFB.c
index 84ed0cb..b33f252 100644
--- a/src/windows/WinMiniFB.c
+++ b/src/windows/WinMiniFB.c
@@ -19,7 +19,7 @@ LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
 {
     LRESULT res = 0;
 
-    SWindowData     *window_data     = (SWindowData *) GetWindowLongPtr(hWnd, GWL_USERDATA);
+    SWindowData     *window_data     = (SWindowData *) GetWindowLongPtr(hWnd, GWLP_USERDATA);
     SWindowData_Win *window_data_win = 0x0;
     if(window_data != 0x0) {
         window_data_win = (SWindowData_Win *) window_data->specific;
diff --git a/tests/multiple_windows.c b/tests/multiple_windows.c
index 4b301c0..29276be 100644
--- a/tests/multiple_windows.c
+++ b/tests/multiple_windows.c
@@ -1,6 +1,7 @@
 #include <MiniFB.h>
 #include <stdio.h>
 #include <stdint.h>
+#define _USE_MATH_DEFINES
 #include <math.h>
 
 #define kUnused(var)    (void) var;
