diff --git a/sowm.c b/sowm.c
index 793826c..e228f01 100644
--- a/sowm.c
+++ b/sowm.c
@@ -58,8 +58,8 @@ void notify_motion(XEvent *e) {
     XMoveResizeWindow(d, mouse.subwindow,
         wx + (mouse.button == 1 ? xd : 0),
         wy + (mouse.button == 1 ? yd : 0),
-        ww + (mouse.button == 3 ? xd : 0),
-        wh + (mouse.button == 3 ? yd : 0));
+        MAX(1, ww + (mouse.button == 3 ? xd : 0)),
+        MAX(1, wh + (mouse.button == 3 ? yd : 0)));
 }
 
 void key_press(XEvent *e) {
diff --git a/sowm.h b/sowm.h
index 750b297..80dad43 100644
--- a/sowm.h
+++ b/sowm.h
@@ -3,6 +3,7 @@
 #define win        (client *t=0, *c=list; c && t!=list->prev; t=c, c=c->next)
 #define ws_save(W) ws_list[W] = list
 #define ws_sel(W)  list = ws_list[ws = W]
+#define MAX(a, b)  ((a) > (b) ? (a) : (b))
 
 #define win_size(W, gx, gy, gw, gh) \
     XGetGeometry(d, W, &(Window){0}, gx, gy, gw, gh, \
@@ -12,7 +13,7 @@
 #define mod_clean(mask) (mask & ~(numlock|LockMask) & \
         (ShiftMask|ControlMask|Mod1Mask|Mod2Mask|Mod3Mask|Mod4Mask|Mod5Mask))
 
-typedef union {
+typedef struct {
     const char** com;
     const int i;
     const Window w;