diff --git a/server/shadow/X11/x11_shadow.c b/server/shadow/X11/x11_shadow.c
index 298c6db4e..c307569aa 100644
--- a/server/shadow/X11/x11_shadow.c
+++ b/server/shadow/X11/x11_shadow.c
@@ -722,14 +722,19 @@ static BOOL x11_shadow_check_resize(x11ShadowSubsystem* subsystem)
 
 		/* Screen size changed. Refresh monitor definitions and trigger screen resize */
 		subsystem->common.numMonitors = x11_shadow_enum_monitors(subsystem->common.monitors, 16);
-		shadow_screen_resize(subsystem->common.server->screen);
-		subsystem->width = attr.width;
-		subsystem->height = attr.height;
+		if (!shadow_screen_resize(subsystem->common.server->screen))
+			return FALSE;
+
+		WINPR_ASSERT(attr.width > 0);
+		WINPR_ASSERT(attr.height > 0);
+
+		subsystem->width = (UINT32)attr.width;
+		subsystem->height = (UINT32)attr.height;
 
 		virtualScreen->left = 0;
 		virtualScreen->top = 0;
-		virtualScreen->right = subsystem->width - 1;
-		virtualScreen->bottom = subsystem->height - 1;
+		virtualScreen->right = attr.width - 1;
+		virtualScreen->bottom = attr.height - 1;
 		virtualScreen->flags = 1;
 		return TRUE;
 	}
diff --git a/server/shadow/shadow_screen.c b/server/shadow/shadow_screen.c
index 8a9e0b304..f5a44d0ba 100644
--- a/server/shadow/shadow_screen.c
+++ b/server/shadow/shadow_screen.c
@@ -119,23 +119,22 @@ void shadow_screen_free(rdpShadowScreen* screen)
 
 BOOL shadow_screen_resize(rdpShadowScreen* screen)
 {
-	int x = 0;
-	int y = 0;
-	int width = 0;
-	int height = 0;
-	MONITOR_DEF* primary = NULL;
-	rdpShadowSubsystem* subsystem = NULL;
-
 	if (!screen)
 		return FALSE;
 
-	subsystem = screen->server->subsystem;
-	primary = &(subsystem->monitors[subsystem->selectedMonitor]);
+	WINPR_ASSERT(screen->server);
 
-	x = primary->left;
-	y = primary->top;
-	width = primary->right - primary->left + 1;
-	height = primary->bottom - primary->top + 1;
+	rdpShadowSubsystem* subsystem = screen->server->subsystem;
+	WINPR_ASSERT(subsystem);
+	WINPR_ASSERT(subsystem->monitors);
+
+	MONITOR_DEF* primary = &(subsystem->monitors[subsystem->selectedMonitor]);
+	WINPR_ASSERT(primary);
+
+	const INT32 x = primary->left;
+	const INT32 y = primary->top;
+	const INT32 width = primary->right - primary->left + 1;
+	const INT32 height = primary->bottom - primary->top + 1;
 
 	WINPR_ASSERT(x >= 0);
 	WINPR_ASSERT(x <= UINT16_MAX);
@@ -145,6 +144,7 @@ BOOL shadow_screen_resize(rdpShadowScreen* screen)
 	WINPR_ASSERT(width <= UINT16_MAX);
 	WINPR_ASSERT(height >= 0);
 	WINPR_ASSERT(height <= UINT16_MAX);
+
 	if (shadow_surface_resize(screen->primary, (UINT16)x, (UINT16)y, (UINT16)width,
 	                          (UINT16)height) &&
 	    shadow_surface_resize(screen->lobby, (UINT16)x, (UINT16)y, (UINT16)width, (UINT16)height))