diff --git a/config/unix-cuda.cmake b/config/unix-cuda.cmake
index be9570107..6bd1e59a4 100644
--- a/config/unix-cuda.cmake
+++ b/config/unix-cuda.cmake
@@ -65,7 +65,7 @@ if(NOT CUDA_FLAGS_INITIALIZED)
       file(READ /etc/redhat-release rhr)
       string(REGEX REPLACE "[^0-9]*([0-9]+).([0-9]+).*" "\\1.\\2" redhat_version "${rhr}")
       # If manually specified (eg. spack), do not add the --gcc-toolchain option
-      if(NOT (CMAKE_CUDA_FLAGS MATCHES "--gcc-toolchain=" OR $ENV{SPACK_CFLAGS} MATCHES
+      if(NOT (CMAKE_CUDA_FLAGS MATCHES "--gcc-toolchain=" OR "$ENV{SPACK_CFLAGS}" MATCHES
                                                              "--gcc-toolchain="))
         string(APPEND CMAKE_CUDA_FLAGS " -Xcompiler")
         if(redhat_version MATCHES "^8.([0-9]+)")
diff --git a/config/unix-xl.cmake b/config/unix-xl.cmake
index e2c58680c..c9c39fac5 100644
--- a/config/unix-xl.cmake
+++ b/config/unix-xl.cmake
@@ -33,7 +33,7 @@ if(NOT CXX_FLAGS_INITIALIZED)
     file(READ /etc/redhat-release rhr)
     string(REGEX REPLACE "[^0-9]*([0-9]+).([0-9]+).*" "\\1.\\2" redhat_version "${rhr}")
     # If manually specified (eg. spack), do not add the --gcc-toolchain option
-    if(NOT (CMAKE_C_FLAGS MATCHES "--gcc-toolchain=" OR $ENV{SPACK_CFLAGS} MATCHES
+    if(NOT (CMAKE_C_FLAGS MATCHES "--gcc-toolchain=" OR "$ENV{SPACK_CFLAGS}" MATCHES
                                                         "--gcc-toolchain="))
       if(redhat_version MATCHES "^8.([0-9]+)")
         string(APPEND CMAKE_C_FLAGS " --gcc-toolchain=/usr/tce/packages/gcc/gcc-11.2.1")