diff --git a/src/gallium/drivers/radeonsi/radeonsi_shader.c b/src/gallium/drivers/radeonsi/radeonsi_shader.c
index 7c57f4c2f3e..704f859efd7 100644
--- a/src/gallium/drivers/radeonsi/radeonsi_shader.c
+++ b/src/gallium/drivers/radeonsi/radeonsi_shader.c
@@ -301,14 +301,8 @@ static void declare_input_fs(
 	/* XXX: Handle all possible interpolation modes */
 	switch (decl->Interp.Interpolate) {
 	case TGSI_INTERPOLATE_COLOR:
-		/* XXX: Flat shading hangs the GPU */
-		if (si_shader_ctx->rctx->queued.named.rasterizer &&
-		    si_shader_ctx->rctx->queued.named.rasterizer->flatshade) {
-#if 0
+		if (si_shader_ctx->key.flatshade) {
 			intr_name = "llvm.SI.fs.interp.constant";
-#else
-			intr_name = "llvm.SI.fs.interp.linear.center";
-#endif
 		} else {
 			if (decl->Interp.Centroid)
 				intr_name = "llvm.SI.fs.interp.persp.centroid";
@@ -317,11 +311,8 @@ static void declare_input_fs(
 		}
 		break;
 	case TGSI_INTERPOLATE_CONSTANT:
-		/* XXX: Flat shading hangs the GPU */
-#if 0
 		intr_name = "llvm.SI.fs.interp.constant";
 		break;
-#endif
 	case TGSI_INTERPOLATE_LINEAR:
 		if (decl->Interp.Centroid)
 			intr_name = "llvm.SI.fs.interp.linear.centroid";
diff --git a/src/gallium/drivers/radeonsi/radeonsi_shader.h b/src/gallium/drivers/radeonsi/radeonsi_shader.h
index 07b2f9fc3e6..f54f67c4988 100644
--- a/src/gallium/drivers/radeonsi/radeonsi_shader.h
+++ b/src/gallium/drivers/radeonsi/radeonsi_shader.h
@@ -82,6 +82,7 @@ struct si_shader_key {
 	unsigned		nr_cbufs:4;
 	unsigned		color_two_side:1;
 	unsigned		alpha_func:3;
+	unsigned		flatshade:1;
 	float			alpha_ref;
 };
 
diff --git a/src/gallium/drivers/radeonsi/si_state.c b/src/gallium/drivers/radeonsi/si_state.c
index 81452ebc231..bb1bacdafbd 100644
--- a/src/gallium/drivers/radeonsi/si_state.c
+++ b/src/gallium/drivers/radeonsi/si_state.c
@@ -421,8 +421,7 @@ static void *si_create_rs_state(struct pipe_context *ctx,
 	rs->offset_units = state->offset_units;
 	rs->offset_scale = state->offset_scale * 12.0f;
 
-	/* XXX: Flat shading hangs the GPU */
-	tmp = S_0286D4_FLAT_SHADE_ENA(0);
+	tmp = S_0286D4_FLAT_SHADE_ENA(1);
 	if (state->sprite_coord_enable) {
 		tmp |= S_0286D4_PNT_SPRITE_ENA(1) |
 			S_0286D4_PNT_SPRITE_OVRD_X(V_0286D4_SPI_PNT_SPRITE_SEL_S) |
@@ -1885,7 +1884,7 @@ static INLINE struct si_shader_key si_shader_selector_key(struct pipe_context *c
 		key.export_16bpc = rctx->export_16bpc;
 		if (rctx->queued.named.rasterizer) {
 			key.color_two_side = rctx->queued.named.rasterizer->two_side;
-			/*key.flatshade = rctx->queued.named.rasterizer->flatshade;*/
+			key.flatshade = rctx->queued.named.rasterizer->flatshade;
 		}
 		if (rctx->queued.named.dsa) {
 			key.alpha_func = rctx->queued.named.dsa->alpha_func;
diff --git a/src/gallium/drivers/radeonsi/si_state_draw.c b/src/gallium/drivers/radeonsi/si_state_draw.c
index 3704410c9bf..61dea74ac12 100644
--- a/src/gallium/drivers/radeonsi/si_state_draw.c
+++ b/src/gallium/drivers/radeonsi/si_state_draw.c
@@ -128,11 +128,6 @@ static void si_pipe_shader_ps(struct pipe_context *ctx, struct si_pipe_shader *s
 			continue;
 		}
 
-		/* XXX: Flat shading hangs the GPU */
-		if (shader->shader.input[i].interpolate == TGSI_INTERPOLATE_CONSTANT ||
-		    (shader->shader.input[i].interpolate == TGSI_INTERPOLATE_COLOR &&
-		     rctx->queued.named.rasterizer->flatshade))
-			have_linear = TRUE;
 		if (shader->shader.input[i].interpolate == TGSI_INTERPOLATE_LINEAR)
 			have_linear = TRUE;
 		if (shader->shader.input[i].interpolate == TGSI_INTERPOLATE_PERSPECTIVE)
@@ -327,15 +322,12 @@ static void si_update_spi_map(struct r600_context *rctx)
 bcolor:
 		tmp = 0;
 
-#if 0
-		/* XXX: Flat shading hangs the GPU */
 		if (name == TGSI_SEMANTIC_POSITION ||
 		    ps->input[i].interpolate == TGSI_INTERPOLATE_CONSTANT ||
 		    (ps->input[i].interpolate == TGSI_INTERPOLATE_COLOR &&
-		     rctx->rasterizer && rctx->rasterizer->flatshade)) {
+		     rctx->ps_shader->current->key.flatshade)) {
 			tmp |= S_028644_FLAT_SHADE(1);
 		}
-#endif
 
 		if (name == TGSI_SEMANTIC_GENERIC &&
 		    rctx->sprite_coord_enable & (1 << ps->input[i].sid)) {