diff --git a/src/mesa/state_tracker/st_atom_constbuf.c b/src/mesa/state_tracker/st_atom_constbuf.c
index f67772d33c4..96f00cef52e 100644
--- a/src/mesa/state_tracker/st_atom_constbuf.c
+++ b/src/mesa/state_tracker/st_atom_constbuf.c
@@ -185,14 +185,11 @@ st_upload_constants(struct st_context *st, struct gl_program *prog)
          }
       }
 
-      st->state.constants[shader_type].ptr = params->ParameterValues;
-      st->state.constants[shader_type].size = paramBytes;
-   }
-   else if (st->state.constants[shader_type].ptr) {
+      st->state.constbuf0_enabled_shader_mask |= 1 << shader_type;
+   } else if (st->state.constbuf0_enabled_shader_mask & (1 << shader_type)) {
       /* Unbind. */
-      st->state.constants[shader_type].ptr = NULL;
-      st->state.constants[shader_type].size = 0;
       cso_set_constant_buffer(st->cso_context, shader_type, 0, NULL);
+      st->state.constbuf0_enabled_shader_mask &= ~(1 << shader_type);
    }
 }
 
diff --git a/src/mesa/state_tracker/st_context.h b/src/mesa/state_tracker/st_context.h
index 8f2a109ab09..ac359096a7c 100644
--- a/src/mesa/state_tracker/st_context.h
+++ b/src/mesa/state_tracker/st_context.h
@@ -202,10 +202,7 @@ struct st_context
       struct pipe_sampler_view *frag_sampler_views[PIPE_MAX_SAMPLERS];
       GLuint num_sampler_views[PIPE_SHADER_TYPES];
       struct pipe_clip_state clip;
-      struct {
-         void *ptr;
-         unsigned size;
-      } constants[PIPE_SHADER_TYPES];
+      unsigned constbuf0_enabled_shader_mask;
       unsigned fb_width;
       unsigned fb_height;
       unsigned fb_num_samples;
diff --git a/src/mesa/state_tracker/st_draw_feedback.c b/src/mesa/state_tracker/st_draw_feedback.c
index adfdffb39bd..efb51cc484e 100644
--- a/src/mesa/state_tracker/st_draw_feedback.c
+++ b/src/mesa/state_tracker/st_draw_feedback.c
@@ -237,8 +237,8 @@ st_feedback_draw_vbo(struct gl_context *ctx,
       _mesa_load_state_parameters(st->ctx, params);
 
    draw_set_mapped_constant_buffer(draw, PIPE_SHADER_VERTEX, 0,
-                                   st->state.constants[PIPE_SHADER_VERTEX].ptr,
-                                   st->state.constants[PIPE_SHADER_VERTEX].size);
+                                   params->ParameterValues,
+                                   params->NumParameterValues * 4);
 
    /* set uniform buffers */
    const struct gl_program *prog = &vp->Base.Base;