diff --git a/share/spack/setup-env.csh b/share/spack/setup-env.csh
index 67357c94e49..c4a2f6a4731 100755
--- a/share/spack/setup-env.csh
+++ b/share/spack/setup-env.csh
@@ -12,6 +12,13 @@
 #    setenv SPACK_ROOT /path/to/spack
 #    source $SPACK_ROOT/share/spack/setup-env.csh
 #
+
+# prevent infinite recursion when spack shells out (e.g., on cray for modules)
+if ($?_sp_initializing) then
+    exit 0
+endif
+setenv _sp_initializing true
+
 if ($?SPACK_ROOT) then
     set _spack_source_file = $SPACK_ROOT/share/spack/setup-env.csh
     set _spack_share_dir   = $SPACK_ROOT/share/spack
@@ -37,3 +44,6 @@ else
     echo "ERROR: Sourcing spack setup-env.csh requires setting SPACK_ROOT to "
     echo "       the root of your spack installation."
 endif
+
+# done: unset sentinel variable as we're no longer initializing
+unsetenv _sp_initializing
diff --git a/share/spack/setup-env.sh b/share/spack/setup-env.sh
index 5968c4c0160..703079988df 100755
--- a/share/spack/setup-env.sh
+++ b/share/spack/setup-env.sh
@@ -39,6 +39,12 @@
 # spack module files.
 ########################################################################
 
+# prevent infinite recursion when spack shells out (e.g., on cray for modules)
+if [ -n "${_sp_initializing:-}" ]; then
+    exit 0
+fi
+export _sp_initializing=true
+
 spack() {
     # Store LD_LIBRARY_PATH variables from spack shell function
     # This is necessary because MacOS System Integrity Protection clears
@@ -358,3 +364,7 @@ _sp_multi_pathadd MODULEPATH "$_sp_tcl_roots"
 if [ "$_sp_shell" = bash ]; then
     source $_sp_share_dir/spack-completion.bash
 fi
+
+# done: unset sentinel variable as we're no longer initializing
+unset _sp_initializing
+export _sp_initializing