diff --git a/Windows/GEDebugger/SimpleGLWindow.h b/Windows/GEDebugger/SimpleGLWindow.h
index c69a0ab997..4aae6d0223 100644
--- a/Windows/GEDebugger/SimpleGLWindow.h
+++ b/Windows/GEDebugger/SimpleGLWindow.h
@@ -77,6 +77,14 @@ struct SimpleGLWindow {
 		return h_;
 	}
 
+	int TexWidth() {
+		return tw_;
+	}
+
+	int TexHeight() {
+		return th_;
+	}
+
 	void GetContentSize(float &x, float &y, float &fw, float &fh);
 
 	static void RegisterClass();
diff --git a/Windows/GEDebugger/VertexPreview.cpp b/Windows/GEDebugger/VertexPreview.cpp
index c76da41ad7..e4ec502aed 100644
--- a/Windows/GEDebugger/VertexPreview.cpp
+++ b/Windows/GEDebugger/VertexPreview.cpp
@@ -177,12 +177,12 @@ void CGEDebugger::UpdatePrimPreview(u32 op) {
 	glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
 	glBlendEquation(GL_FUNC_ADD);
 	glBindTexture(GL_TEXTURE_2D, 0);
-	glViewport(x, -y, fw, fh);
+	glViewport(x, y, fw, fh);
 	glScissor(x, y, fw, fh);
 	BindPreviewProgram(previewProgram);
 
 	Matrix4x4 ortho;
-	ortho.setOrtho(0, fw, fh, 0, -1, 1);
+	ortho.setOrtho(0, frameWindow->TexWidth(), frameWindow->TexHeight(), 0, -1, 1);
 	glUniformMatrix4fv(previewProgram->u_viewproj, 1, GL_FALSE, ortho.getReadPtr());
 	glEnableVertexAttribArray(previewProgram->a_position);
 	glVertexAttribPointer(previewProgram->a_position, 3, GL_FLOAT, GL_FALSE, sizeof(GPUDebugVertex), (float *)vertices.data() + 2);