diff --git a/src/compiler/nir/nir_lower_passthrough_edgeflags.c b/src/compiler/nir/nir_lower_passthrough_edgeflags.c
index 1fd2cd20014..e6d0b14f26b 100644
--- a/src/compiler/nir/nir_lower_passthrough_edgeflags.c
+++ b/src/compiler/nir/nir_lower_passthrough_edgeflags.c
@@ -96,5 +96,9 @@ lower_impl(nir_function_impl *impl)
 
 void nir_lower_passthrough_edgeflags(nir_shader *shader)
 {
+   assert(shader->info.stage == MESA_SHADER_VERTEX);
+
+   shader->info.vs.needs_edge_flag = true;
+
    lower_impl(nir_shader_get_entrypoint(shader));
 }
diff --git a/src/compiler/shader_info.h b/src/compiler/shader_info.h
index b3aabb9f054..91421db9b74 100644
--- a/src/compiler/shader_info.h
+++ b/src/compiler/shader_info.h
@@ -297,6 +297,9 @@ typedef struct shader_info {
 
          /* True if the shader writes position in window space coordinates pre-transform */
          bool window_space_position:1;
+
+         /** Is an edge flag input needed? */
+         bool needs_edge_flag:1;
       } vs;
 
       struct {
diff --git a/src/gallium/drivers/iris/iris_program.c b/src/gallium/drivers/iris/iris_program.c
index 840a5cb28d4..858294ad2d9 100644
--- a/src/gallium/drivers/iris/iris_program.c
+++ b/src/gallium/drivers/iris/iris_program.c
@@ -2441,6 +2441,7 @@ iris_create_uncompiled_shader(struct iris_screen *screen,
    simple_mtx_init(&ish->lock, mtx_plain);
 
    NIR_PASS(ish->needs_edge_flag, nir, iris_fix_edge_flags);
+   assert(ish->needs_edge_flag == nir->info.vs.needs_edge_flag);
 
    brw_preprocess_nir(screen->compiler, nir, NULL);