diff --git a/src/vrend_decode.c b/src/vrend_decode.c
index be5777e..a5467e3 100644
--- a/src/vrend_decode.c
+++ b/src/vrend_decode.c
@@ -219,6 +219,10 @@ static int vrend_decode_set_constant_buffer(struct vrend_decode_ctx *ctx, uint16
 
    shader = get_buf_entry(ctx, VIRGL_SET_CONSTANT_BUFFER_SHADER_TYPE);
    index = get_buf_entry(ctx, VIRGL_SET_CONSTANT_BUFFER_INDEX);
+
+   if (shader >= PIPE_SHADER_TYPES)
+      return EINVAL;
+
    vrend_set_constants(ctx->grctx, shader, index, nc, get_buf_ptr(ctx, VIRGL_SET_CONSTANT_BUFFER_DATA_START));
    return 0;
 }