diff --git a/plugins/GSdx/GSRendererOGL.cpp b/plugins/GSdx/GSRendererOGL.cpp
index 600d2a590c..e1a129bd5f 100644
--- a/plugins/GSdx/GSRendererOGL.cpp
+++ b/plugins/GSdx/GSRendererOGL.cpp
@@ -751,39 +751,52 @@ void GSRendererOGL::DrawPrims(GSTexture* rt, GSTexture* ds, GSTextureCache::Sour
 #endif
 	}
 
-	// Post-processing hack
+	// Upscaling hack to avoid various line/grid issues
 	if (UserHacks_merge_sprite && tex && tex->m_target && (m_vt.m_primclass == GS_SPRITE_CLASS)) {
 		if (PRIM->FST && GSLocalMemory::m_psm[tex->m_TEX0.PSM].fmt < 2 && ((m_vt.m_eq.value & 0xCFFFF) == 0xCFFFF)) {
-#ifdef ENABLE_OGL_DEBUG
-			const GSVector4 delta_p = m_vt.m_max.p - m_vt.m_min.p;
-			const GSVector4 delta_t = m_vt.m_max.t - m_vt.m_min.t;
-			GL_INS("PP SAMPLER: Dp %f %f Dt %f %f", delta_p.x, delta_p.y, delta_t.x, delta_t.y);
+
+			// Ideally the hack ought to be enabled in a true paving mode only. I don't know how to do it accurately
+			// neither in a fast way. So instead let's just take the hypothesis that all sprites must have the same
+			// size.
+			// Tested on Tekken 5.
+			GSVertex* v = &m_vertex.buff[0];
+			bool is_paving = true;
+			// SSE optimization: shuffle m[1] to have (4*32 bits) X, Y, U, V
+			int first_dpX = v[1].XYZ.X - v[0].XYZ.X;
+			int first_dpU = v[1].U - v[0].U;
+			for (int i = 0; i < m_vertex.next; i += 2) {
+				int dpX = v[i+1].XYZ.X - v[i].XYZ.X;
+				int dpU = v[i+1].U - v[i].U;
+				if (dpX != first_dpX || dpU != first_dpU) {
+					is_paving = false;
+					break;
+				}
+			}
+
+#if 0
+			GSVector4 delta_p = m_vt.m_max.p - m_vt.m_min.p;
+			GSVector4 delta_t = m_vt.m_max.t - m_vt.m_min.t;
+			bool is_blit = PrimitiveOverlap() == PRIM_OVERLAP_NO;
+			GL_INS("PP SAMPLER: Dp %f %f Dt %f %f. Is blit %d, is paving %d, count %d", delta_p.x, delta_p.y, delta_t.x, delta_t.y, is_blit, is_paving, m_vertex.tail);
 #endif
-			//fprintf(stderr, "SAMPLER: Dp %f %f Dt %f %f\n", delta_p.x, delta_p.y, delta_t.x, delta_t.y);
 
-			GSVertex* s = &m_vertex.buff[0];
-			//fprintf(stderr, "Before %d %d => %d %d \n", s[0].XYZ.X, s[0].XYZ.Y, s[1].XYZ.Y, s[1].XYZ.Y);
-			//fprintf(stderr, "SAMPLER: p %f %f OFFSET %d\n", m_vt.m_min.p.x, m_vt.m_max.p.x, m_context->XYOFFSET.OFX);
+			if (is_paving) {
+				// Replace all sprite with a single fullscreen sprite.
+				GSVertex* s = &m_vertex.buff[0];
 
-			s[0].XYZ.X = (16.0f * m_vt.m_min.p.x) + m_context->XYOFFSET.OFX;
-			s[1].XYZ.X = (16.0f * m_vt.m_max.p.x) + m_context->XYOFFSET.OFX;
-			s[0].XYZ.Y = (16.0f * m_vt.m_min.p.y) + m_context->XYOFFSET.OFY;
-			s[1].XYZ.Y = (16.0f * m_vt.m_max.p.y) + m_context->XYOFFSET.OFY;
+				s[0].XYZ.X = (16.0f * m_vt.m_min.p.x) + m_context->XYOFFSET.OFX;
+				s[1].XYZ.X = (16.0f * m_vt.m_max.p.x) + m_context->XYOFFSET.OFX;
+				s[0].XYZ.Y = (16.0f * m_vt.m_min.p.y) + m_context->XYOFFSET.OFY;
+				s[1].XYZ.Y = (16.0f * m_vt.m_max.p.y) + m_context->XYOFFSET.OFY;
 
-			//fprintf(stderr, "After %d %d => %d %d \n", s[0].XYZ.X, s[0].XYZ.Y, s[1].XYZ.Y, s[1].XYZ.Y);
+				s[0].U     = 16.0f * m_vt.m_min.t.x;
+				s[0].V     = 16.0f * m_vt.m_min.t.y;
+				s[1].U     = 16.0f * m_vt.m_max.t.x;
+				s[1].V     = 16.0f * m_vt.m_max.t.y;
 
-			//fprintf(stderr, "Before %d %d => %d %d \n", s[0].U, s[0].V, s[1].U, s[1].V);
-
-			s[0].U     = 16.0f * m_vt.m_min.t.x;
-			s[0].V     = 16.0f * m_vt.m_min.t.y;
-			s[1].U     = 16.0f * m_vt.m_max.t.x;
-			s[1].V     = 16.0f * m_vt.m_max.t.y;
-
-			//fprintf(stderr, "After %d %d => %d %d \n", s[0].U, s[0].V, s[1].U, s[1].V);
-
-			m_vertex.head = m_vertex.tail = m_vertex.next = 2;
-			m_index.tail = 2;
-			//exit(0);
+				m_vertex.head = m_vertex.tail = m_vertex.next = 2;
+				m_index.tail = 2;
+			}
 		}
 	}