diff --git a/GPU/Common/FramebufferCommon.cpp b/GPU/Common/FramebufferCommon.cpp
index fadf926334..d0ae91c2d0 100644
--- a/GPU/Common/FramebufferCommon.cpp
+++ b/GPU/Common/FramebufferCommon.cpp
@@ -2052,19 +2052,34 @@ void FramebufferManagerCommon::PackFramebufferSync_(VirtualFramebuffer *vfb, int
 		return;
 	}
 
+	if (w <= 0 || h <= 0) {
+		ERROR_LOG(G3D, "Bad inputs to PackFramebufferSync_: %d %d %d %d", x, y, w, h);
+		return;
+	}
+
 	const u32 fb_address = (0x04000000) | vfb->fb_address;
 
 	Draw::DataFormat destFormat = GEFormatToThin3D(vfb->format);
 	const int dstBpp = (int)DataFormatSizeInBytes(destFormat);
 
 	const int dstByteOffset = (y * vfb->fb_stride + x) * dstBpp;
+
+	if (!Memory::IsValidRange(fb_address + dstByteOffset, ((h - 1) * vfb->fb_stride + w) * dstBpp)) {
+		ERROR_LOG(G3D, "PackFramebufferSync_ would write outside of memory, ignoring");
+		return;
+	}
+
 	u8 *destPtr = Memory::GetPointer(fb_address + dstByteOffset);
 
 	// We always need to convert from the framebuffer native format.
 	// Right now that's always 8888.
-	DEBUG_LOG(G3D, "Reading framebuffer to mem, fb_address = %08x", fb_address);
+	DEBUG_LOG(G3D, "Reading framebuffer to mem, fb_address = %08x, ptr=%p", fb_address, destPtr);
 
-	draw_->CopyFramebufferToMemorySync(vfb->fbo, Draw::FB_COLOR_BIT, x, y, w, h, destFormat, destPtr, vfb->fb_stride);
+	if (destPtr) {
+		draw_->CopyFramebufferToMemorySync(vfb->fbo, Draw::FB_COLOR_BIT, x, y, w, h, destFormat, destPtr, vfb->fb_stride);
+	} else {
+		ERROR_LOG(G3D, "PackFramebufferSync_: Tried to readback to bad address %08x (stride = %d)", fb_address + dstByteOffset, vfb->fb_stride);
+	}
 
 	// A new command buffer will begin after CopyFrameBufferToMemorySync, so we need to trigger
 	// updates of any dynamic command buffer state by dirtying some stuff.
diff --git a/ext/native/thin3d/GLRenderManager.cpp b/ext/native/thin3d/GLRenderManager.cpp
index ab1cb8f675..413e4155dc 100644
--- a/ext/native/thin3d/GLRenderManager.cpp
+++ b/ext/native/thin3d/GLRenderManager.cpp
@@ -334,6 +334,8 @@ void GLRenderManager::BlitFramebuffer(GLRFramebuffer *src, GLRect2D srcRect, GLR
 }
 
 bool GLRenderManager::CopyFramebufferToMemorySync(GLRFramebuffer *src, int aspectBits, int x, int y, int w, int h, Draw::DataFormat destFormat, uint8_t *pixels, int pixelStride) {
+	_assert_(pixels);
+
 	GLRStep *step = new GLRStep{ GLRStepType::READBACK };
 	step->readback.src = src;
 	step->readback.srcRect = { x, y, w, h };
@@ -365,6 +367,7 @@ bool GLRenderManager::CopyFramebufferToMemorySync(GLRFramebuffer *src, int aspec
 
 void GLRenderManager::CopyImageToMemorySync(GLRTexture *texture, int mipLevel, int x, int y, int w, int h, Draw::DataFormat destFormat, uint8_t *pixels, int pixelStride) {
 	_assert_(texture);
+	_assert_(pixels);
 	GLRStep *step = new GLRStep{ GLRStepType::READBACK_IMAGE };
 	step->readback_image.texture = texture;
 	step->readback_image.mipLevel = mipLevel;