diff --git a/lib/simmux_gpu.h b/lib/simmux_gpu.h
index 9b08ac48..1f0bb592 100644
--- a/lib/simmux_gpu.h
+++ b/lib/simmux_gpu.h
@@ -18,12 +18,12 @@
 #ifdef __CUSTATEVEC__
 # include "simulator_custatevec.h"
   namespace qsim {
-    using SimulatorGpu = SimulatorCuStateVec;
+    using SimulatorGpu = SimulatorCuStateVec<>;
   }
 #else
 # include "simulator_cuda.h"
   namespace qsim {
-    using SimulatorGpu = SimulatorCUDA;
+    using SimulatorGpu = SimulatorCUDA<>;
   }
 #endif
 
diff --git a/third_party/cuquantum/cuquantum_configure.bzl b/third_party/cuquantum/cuquantum_configure.bzl
index d4846ad4..19feb557 100644
--- a/third_party/cuquantum/cuquantum_configure.bzl
+++ b/third_party/cuquantum/cuquantum_configure.bzl
@@ -196,7 +196,12 @@ def _symlink_genrule_for_dir(
 
 
 def _cuquantum_pip_impl(repository_ctx):
-    cuquantum_root = repository_ctx.os.environ[_CUQUANTUM_ROOT]
+    if _CUQUANTUM_ROOT in repository_ctx.os.environ:
+      cuquantum_root = repository_ctx.os.environ[_CUQUANTUM_ROOT]
+    else:
+      repository_ctx.os.environ[_CUQUANTUM_ROOT] = ""
+      cuquantum_root = ""
+
     if cuquantum_root == "":
       cuquantum_header_path = _find_file(repository_ctx, "custatevec.h")
       cuquantum_header_path = cuquantum_header_path[:cuquantum_header_path.find("/custatevec.h")]