diff --git a/ext/native/thin3d/VulkanRenderManager.h b/ext/native/thin3d/VulkanRenderManager.h
index a01482b69eb4..cfac32d75c9c 100644
--- a/ext/native/thin3d/VulkanRenderManager.h
+++ b/ext/native/thin3d/VulkanRenderManager.h
@@ -118,6 +118,7 @@ class VulkanRenderManager {
 
 	void SetViewport(const VkViewport &vp) {
 		_dbg_assert_(G3D, curRenderStep_ && curRenderStep_->stepType == VKRStepType::RENDER);
+		_dbg_assert_(G3D, (int)vp.width >= 0);
 		VkRenderData data{ VKRRenderCommand::VIEWPORT };
 		data.viewport.vp.x = vp.x;
 		data.viewport.vp.y = vp.y;
@@ -132,6 +133,8 @@ class VulkanRenderManager {
 
 	void SetScissor(const VkRect2D &rc) {
 		_dbg_assert_(G3D, curRenderStep_ && curRenderStep_->stepType == VKRStepType::RENDER);
+		_dbg_assert_(G3D, (int)rc.extent.width >= 0);
+		_dbg_assert_(G3D, (int)rc.extent.height >= 0);
 		VkRenderData data{ VKRRenderCommand::SCISSOR };
 		data.scissor.scissor = rc;
 		curRenderStep_->commands.push_back(data);
diff --git a/ext/native/ui/ui_context.cpp b/ext/native/ui/ui_context.cpp
index 0106888ec468..b5f7ba204fa3 100644
--- a/ext/native/ui/ui_context.cpp
+++ b/ext/native/ui/ui_context.cpp
@@ -1,4 +1,7 @@
 #include "ppsspp_config.h"
+
+#include <algorithm>
+
 #include "base/display.h"
 #include "ui/ui.h"
 #include "ui/view.h"
@@ -111,8 +114,8 @@ void UIContext::ActivateTopScissor() {
 		bounds = scissorStack_.back();
 		int x = floorf(scale_x * bounds.x);
 		int y = floorf(scale_y * bounds.y);
-		int w = ceilf(scale_x * bounds.w);
-		int h = ceilf(scale_y * bounds.h);
+		int w = std::max(0.0f, ceilf(scale_x * bounds.w));
+		int h = std::max(0.0f, ceilf(scale_y * bounds.h));
 		draw_->SetScissorRect(x, y, w, h);
 	} else {
 		// Avoid rounding errors