diff --git a/.github/workflows/scripts/test_init_scripts.sh b/.github/workflows/scripts/test_init_scripts.sh
index b96ef9cf..722d19a8 100755
--- a/.github/workflows/scripts/test_init_scripts.sh
+++ b/.github/workflows/scripts/test_init_scripts.sh
@@ -150,6 +150,11 @@ for shell in ${SHELLS[@]}; do
         pattern="{EESSI/${EESSI_VERSION}} "
         assert_raises 'echo "$TEST_EESSI_PS1_UPDATE" | grep "$pattern"'
         assert_raises 'echo "$TEST_EESSI_NO_PS1_UPDATE" | grep "$pattern"' 1
+        # Also check when we explicitly ask for it not to be updated
+        TEST_EESSI_EXPLICIT_NO_PS1_UPDATE=$($shell -c "unset PS1 ; PS1='test> ' ; export EESSI_MODULE_UPDATE_PS1=0 ; . init/lmod/$shell 2>/dev/null ; echo \"\$PS1\"")
+        TEST_EESSI_EXPLICIT_NO_PS1_UPDATE_CALLED_TWICE=$($shell -c "unset PS1 ; PS1='$ ' ; export EESSI_MODULE_UPDATE_PS1=0 ; . init/lmod/$shell 2>/dev/null ; . init/lmod/$shell 2>/dev/null ; echo \"\$PS1\"")
+        assert_raises 'echo "$TEST_EESSI_EXPLICIT_NO_PS1_UPDATE" | grep "$pattern"' 1
+        assert_raises 'echo "$TEST_EESSI_EXPLICIT_NO_PS1_UPDATE_CALLED_TWICE" | grep "$pattern"' 1
     fi
 
     # End Test Suite
diff --git a/init/lmod/sh b/init/lmod/sh
index e405c002..5da34fc2 100644
--- a/init/lmod/sh
+++ b/init/lmod/sh
@@ -25,7 +25,7 @@
 # - The EESSI module also listens to environment variables so that it can be silently configured by a site
 #   - EESSI_MODULE_FAMILY_NAME: use the value of the environment variable to set an Lmod family for the EESSI module
 #   - EESSI_MODULE_STICKY: make the EESSI module sticky
-#   - EESSI_MODULE_UPDATE_PS1: have the EESSI module update PS1 to give a prompt that is prepended with "{EESSI/...} " (requires exporting PS1)
+#   - EESSI_MODULE_UPDATE_PS1: set to 1 (by default), the EESSI module prepends  "{EESSI/...} " to PS1 (the shell prompt). Set to 0, PS1 remains unmodified.
 #  (- EESSI_MODULE_DEBUG_INIT: enable debug print statements when loading the EESSI module)
 #
 # Effects:
@@ -97,8 +97,14 @@ if [ -z "$__Init_EESSI_Default_Modules" ]; then
     # For the shells that use PS1 for the prompt, let's add the trigger to enable updating that by default
     # (in an interactive shell PS1 is likely unset, so let's only do this if it is set)
     if [ -n "$PS1" ]; then
-        export PS1
-        export EESSI_MODULE_UPDATE_PS1=1
+        if [ "${EESSI_MODULE_UPDATE_PS1-}" = "0" ] ; then
+            # For certainty, we now unset it to guarantee it is not picked up by the EESSI module
+            # (this guarantees PS1 is not updated, even if it is exported externally to this script)
+            unset EESSI_MODULE_UPDATE_PS1
+        else
+            export EESSI_MODULE_UPDATE_PS1=1
+            export PS1
+        fi
     fi
 
     # Figure out which shell was used to source this script, which we then use to source the corresponding