diff --git a/src/mesa/main/genmipmap.c b/src/mesa/main/genmipmap.c
index 8bf3b1ad568..bcb8ac9c407 100644
--- a/src/mesa/main/genmipmap.c
+++ b/src/mesa/main/genmipmap.c
@@ -160,6 +160,7 @@ generate_texture_mipmap(struct gl_context *ctx,
        */
       if (ctx->API == API_OPENGLES2 && ctx->Version < 30 &&
           _mesa_is_format_compressed(srcImage->TexFormat)) {
+         _mesa_unlock_texture(ctx, texObj);
          _mesa_error(ctx, GL_INVALID_OPERATION, "generate mipmaps on compressed texture");
          return;
       }