diff --git a/GPU/Common/FramebufferCommon.cpp b/GPU/Common/FramebufferCommon.cpp
index 7e1f9e9ca0..f97b2117a3 100644
--- a/GPU/Common/FramebufferCommon.cpp
+++ b/GPU/Common/FramebufferCommon.cpp
@@ -17,6 +17,7 @@
 
 #include <algorithm>
 #include <sstream>
+#include <cassert>
 
 #include "ext/native/thin3d/thin3d.h"
 #include "base/timeutil.h"
@@ -213,7 +214,7 @@ void FramebufferManagerCommon::EstimateDrawingSize(u32 fb_address, GEBufferForma
 	static const int MAX_FRAMEBUF_HEIGHT = 512;
 
 	// Games don't always set any of these.  Take the greatest parameter that looks valid based on stride.
-	if (viewport_width > 4 && viewport_width <= fb_stride) {
+	if (viewport_width > 4 && viewport_width <= fb_stride && viewport_height > 0) {
 		drawing_width = viewport_width;
 		drawing_height = viewport_height;
 		// Some games specify a viewport with 0.5, but don't have VRAM for 273.  480x272 is the buffer size.
@@ -300,8 +301,19 @@ void GetFramebufferHeuristicInputs(FramebufferHeuristicParams *params, const GPU
 	params->isModeThrough = gstate.isModeThrough();
 
 	// Viewport-X1 and Y1 are not the upper left corner, but half the width/height. A bit confusing.
-	params->viewportWidth = (int)(fabsf(gstate.getViewportXScale()*2.0f));
-	params->viewportHeight = (int)(fabsf(gstate.getViewportYScale()*2.0f));
+	float vpx = gstate.getViewportXScale();
+	float vpy = gstate.getViewportYScale();
+
+	// Work around problem in F1 Grand Prix, where it draws in through mode with a bogus viewport.
+	// We set bad values to 0 which causes the framebuffer size heuristic to rely on the other parameters instead.
+	if (isnan(vpx) || vpx > 10000000.0f) {
+		vpx = 0.f;
+	}
+	if (isnan(vpy) || vpy > 10000000.0f) {
+		vpy = 0.f;
+	}
+	params->viewportWidth = (int)(fabsf(vpx) * 2.0f);
+	params->viewportHeight = (int)(fabsf(vpy) * 2.0f);
 	params->regionWidth = gstate.getRegionX2() + 1;
 	params->regionHeight = gstate.getRegionY2() + 1;
 	params->scissorWidth = gstate.getScissorX2() + 1;
@@ -1108,7 +1120,9 @@ void FramebufferManagerCommon::DecimateFBOs() {
 	}
 }
 
-void FramebufferManagerCommon::ResizeFramebufFBO(VirtualFramebuffer *vfb, u16 w, u16 h, bool force, bool skipCopy) {
+void FramebufferManagerCommon::ResizeFramebufFBO(VirtualFramebuffer *vfb, int w, int h, bool force, bool skipCopy) {
+	assert(w > 0);
+	assert(h > 0);
 	VirtualFramebuffer old = *vfb;
 
 	int oldWidth = vfb->bufferWidth;
@@ -1123,8 +1137,8 @@ void FramebufferManagerCommon::ResizeFramebufFBO(VirtualFramebuffer *vfb, u16 w,
 		}
 
 		// In case it gets thin and wide, don't resize down either side.
-		vfb->bufferWidth = std::max(vfb->bufferWidth, w);
-		vfb->bufferHeight = std::max(vfb->bufferHeight, h);
+		vfb->bufferWidth = std::max((int)vfb->bufferWidth, w);
+		vfb->bufferHeight = std::max((int)vfb->bufferHeight, h);
 	}
 
 	SetRenderSize(vfb);
diff --git a/GPU/Common/FramebufferCommon.h b/GPU/Common/FramebufferCommon.h
index 62befe6913..75224a0cc5 100644
--- a/GPU/Common/FramebufferCommon.h
+++ b/GPU/Common/FramebufferCommon.h
@@ -338,7 +338,7 @@ protected:
 	virtual void ReformatFramebufferFrom(VirtualFramebuffer *vfb, GEBufferFormat old) = 0;
 	virtual void BlitFramebufferDepth(VirtualFramebuffer *src, VirtualFramebuffer *dst) = 0;
 
-	void ResizeFramebufFBO(VirtualFramebuffer *vfb, u16 w, u16 h, bool force = false, bool skipCopy = false);
+	void ResizeFramebufFBO(VirtualFramebuffer *vfb, int w, int h, bool force = false, bool skipCopy = false);
 	void ShowScreenResolution();
 
 	bool ShouldDownloadFramebuffer(const VirtualFramebuffer *vfb) const;
diff --git a/ext/native/thin3d/VulkanRenderManager.cpp b/ext/native/thin3d/VulkanRenderManager.cpp
index 1d67e3fe49..bd9692c55e 100644
--- a/ext/native/thin3d/VulkanRenderManager.cpp
+++ b/ext/native/thin3d/VulkanRenderManager.cpp
@@ -318,7 +318,9 @@ void VulkanRenderManager::BindFramebufferAsRenderTarget(VKRFramebuffer *fb, VKRR
 		curRenderStep_ = nullptr;
 	}
 	if (curRenderStep_ && curRenderStep_->commands.size() == 0) {
+#ifdef _DEBUG
 		ILOG("Empty render step. Usually happens after uploading pixels..");
+#endif
 	}
 
 	VKRStep *step = new VKRStep{ VKRStepType::RENDER };