diff --git a/src/dd.c b/src/dd.c
index db4bdf2..cb1bb3d 100644
--- a/src/dd.c
+++ b/src/dd.c
@@ -1,4 +1,5 @@
 #include <windows.h>
+#include <math.h>
 #include "ddraw.h"
 #include "IDirectDraw.h"
 #include "dd.h"
@@ -805,7 +806,7 @@ HRESULT dd_SetDisplayMode(DWORD dwWidth, DWORD dwHeight, DWORD dwBPP, DWORD dwFl
     {
         g_ddraw->render.viewport.width = g_ddraw->render.width;
         g_ddraw->render.viewport.height =
-            (int)(((float)g_ddraw->height / g_ddraw->width) * g_ddraw->render.viewport.width);
+            (int)roundf(((float)g_ddraw->height / g_ddraw->width) * g_ddraw->render.viewport.width);
 
         if (g_ddraw->render.viewport.height > g_ddraw->render.height)
         {
diff --git a/src/utils.c b/src/utils.c
index 3e2d686..2fbd72d 100644
--- a/src/utils.c
+++ b/src/utils.c
@@ -1,5 +1,6 @@
 #include <windows.h>
 #include <intrin.h>
+#include <math.h>
 #include "ddraw.h"
 #include "debug.h"
 #include "dd.h"
@@ -381,11 +382,11 @@ void util_toggle_maximize()
             dst_rc.top = 0;
             dst_rc.left = 0;
             dst_rc.right = w;
-            dst_rc.bottom = (LONG)(((float)g_ddraw->height / g_ddraw->width) * w);
+            dst_rc.bottom = (LONG)roundf(((float)g_ddraw->height / g_ddraw->width) * w);
 
             if (dst_rc.bottom > h)
             {
-                dst_rc.right = (LONG)(((float)dst_rc.right / dst_rc.bottom) * h);
+                dst_rc.right = (LONG)roundf(((float)dst_rc.right / dst_rc.bottom) * h);
                 dst_rc.bottom = h;
             }
 
diff --git a/src/wndproc.c b/src/wndproc.c
index d6f5543..c0886c2 100644
--- a/src/wndproc.c
+++ b/src/wndproc.c
@@ -324,19 +324,19 @@ LRESULT CALLBACK fake_WndProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam
                     case WMSZ_LEFT:
                     case WMSZ_RIGHT:
                     {
-                        windowrc->bottom += (LONG)(scaleH * clientrc.right - clientrc.bottom);
+                        windowrc->bottom += (LONG)roundf(scaleH * clientrc.right - clientrc.bottom);
                         break;
                     }
                     case WMSZ_TOP:
                     case WMSZ_BOTTOM:
                     {
-                        windowrc->right += (LONG)(scaleW * clientrc.bottom - clientrc.right);
+                        windowrc->right += (LONG)roundf(scaleW * clientrc.bottom - clientrc.right);
                         break;
                     }
                     case WMSZ_TOPRIGHT:
                     case WMSZ_TOPLEFT:
                     {
-                        windowrc->top -= (LONG)(scaleH * clientrc.right - clientrc.bottom);
+                        windowrc->top -= (LONG)roundf(scaleH * clientrc.right - clientrc.bottom);
                         break;
                     }
                     }