diff --git a/ci/lib.sh b/ci/lib.sh
index 288a5b3884..fd799ae663 100755
--- a/ci/lib.sh
+++ b/ci/lib.sh
@@ -184,7 +184,7 @@ osx-clang|osx-gcc)
 	export GIT_SKIP_TESTS="t9810 t9816"
 	;;
 GIT_TEST_GETTEXT_POISON)
-	export GIT_TEST_GETTEXT_POISON=YesPlease
+	export GIT_TEST_GETTEXT_POISON=true
 	;;
 esac
 
diff --git a/config.c b/config.c
index 374cb33005..b985d60fa4 100644
--- a/config.c
+++ b/config.c
@@ -956,6 +956,15 @@ static void die_bad_number(const char *name, const char *value)
 	if (!value)
 		value = "";
 
+	if (!strcmp(name, "GIT_TEST_GETTEXT_POISON"))
+		/*
+		 * We explicitly *don't* use _() here since it would
+		 * cause an infinite loop with _() needing to call
+		 * use_gettext_poison(). This is why marked up
+		 * translations with N_() above.
+		 */
+		die(bad_numeric, value, name, error_type);
+
 	if (!(cf && cf->name))
 		die(_(bad_numeric), value, name, _(error_type));
 
diff --git a/gettext.c b/gettext.c
index d4021d690c..5c71f4c8b9 100644
--- a/gettext.c
+++ b/gettext.c
@@ -50,10 +50,8 @@ const char *get_preferred_languages(void)
 int use_gettext_poison(void)
 {
 	static int poison_requested = -1;
-	if (poison_requested == -1) {
-		const char *v = getenv("GIT_TEST_GETTEXT_POISON");
-		poison_requested = v && strlen(v) ? 1 : 0;
-	}
+	if (poison_requested == -1)
+		poison_requested = git_env_bool("GIT_TEST_GETTEXT_POISON", 0);
 	return poison_requested;
 }
 
diff --git a/git-sh-i18n.sh b/git-sh-i18n.sh
index e1d917fd27..8eef60b43f 100644
--- a/git-sh-i18n.sh
+++ b/git-sh-i18n.sh
@@ -17,7 +17,9 @@ export TEXTDOMAINDIR
 
 # First decide what scheme to use...
 GIT_INTERNAL_GETTEXT_SH_SCHEME=fallthrough
-if test -n "$GIT_TEST_GETTEXT_POISON"
+if test -n "$GIT_TEST_GETTEXT_POISON" &&
+	    git env--helper --type=bool --default=0 --exit-code \
+		GIT_TEST_GETTEXT_POISON
 then
 	GIT_INTERNAL_GETTEXT_SH_SCHEME=poison
 elif test -n "@@USE_GETTEXT_SCHEME@@"
diff --git a/po/README b/po/README
index aa704ffcb7..07595d369b 100644
--- a/po/README
+++ b/po/README
@@ -293,7 +293,7 @@ To smoke out issues like these, Git tested with a translation mode that
 emits gibberish on every call to gettext. To use it run the test suite
 with it, e.g.:
 
-    cd t && GIT_TEST_GETTEXT_POISON=YesPlease prove -j 9 ./t[0-9]*.sh
+    cd t && GIT_TEST_GETTEXT_POISON=true prove -j 9 ./t[0-9]*.sh
 
 If tests break with it you should inspect them manually and see if
 what you're translating is sane, i.e. that you're not translating
diff --git a/t/README b/t/README
index 9747971d58..9a131f472e 100644
--- a/t/README
+++ b/t/README
@@ -343,8 +343,8 @@ whether this mode is active, and e.g. skip some tests that are hard to
 refactor to deal with it. The "SYMLINKS" prerequisite is currently
 excluded as so much relies on it, but this might change in the future.
 
-GIT_TEST_GETTEXT_POISON=<non-empty?> turns all strings marked for
-translation into gibberish if non-empty (think "test -n"). Used for
+GIT_TEST_GETTEXT_POISON=<boolean> turns all strings marked for
+translation into gibberish if true. Used for
 spotting those tests that need to be marked with a C_LOCALE_OUTPUT
 prerequisite when adding more strings for translation. See "Testing
 marked strings" in po/README for details.
diff --git a/t/t0017-env-helper.sh b/t/t0017-env-helper.sh
index 709bbbd275..c1ecf6aeac 100755
--- a/t/t0017-env-helper.sh
+++ b/t/t0017-env-helper.sh
@@ -80,4 +80,20 @@ test_expect_success 'env--helper --type=ulong' '
 	test_must_be_empty actual.err
 '
 
+test_expect_success 'env--helper reads config thanks to trace2' '
+	mkdir home &&
+	git config -f home/.gitconfig include.path cycle &&
+	git config -f home/cycle include.path .gitconfig &&
+
+	test_must_fail \
+		env HOME="$(pwd)/home" GIT_TEST_GETTEXT_POISON=false \
+		git config -l 2>err &&
+	grep "exceeded maximum include depth" err &&
+
+	test_must_fail \
+		env HOME="$(pwd)/home" GIT_TEST_GETTEXT_POISON=true \
+		git -C cycle env--helper --type=bool --default=0 --exit-code GIT_TEST_GETTEXT_POISON 2>err &&
+	grep "# GETTEXT POISON #" err
+'
+
 test_done
diff --git a/t/t0205-gettext-poison.sh b/t/t0205-gettext-poison.sh
index a06269f38a..f9fa16ad83 100755
--- a/t/t0205-gettext-poison.sh
+++ b/t/t0205-gettext-poison.sh
@@ -5,7 +5,7 @@
 
 test_description='Gettext Shell poison'
 
-GIT_TEST_GETTEXT_POISON=YesPlease
+GIT_TEST_GETTEXT_POISON=true
 export GIT_TEST_GETTEXT_POISON
 . ./lib-gettext.sh
 
@@ -31,4 +31,9 @@ test_expect_success 'eval_gettext: our eval_gettext() fallback has poison semant
     test_cmp expect actual
 '
 
+test_expect_success "gettext: invalid GIT_TEST_GETTEXT_POISON value doesn't infinitely loop" "
+	test_must_fail env GIT_TEST_GETTEXT_POISON=xyz git version 2>error &&
+	grep \"fatal: bad numeric config value 'xyz' for 'GIT_TEST_GETTEXT_POISON': invalid unit\" error
+"
+
 test_done
diff --git a/t/t1305-config-include.sh b/t/t1305-config-include.sh
index 6b388ba2d0..de294c990e 100755
--- a/t/t1305-config-include.sh
+++ b/t/t1305-config-include.sh
@@ -314,7 +314,7 @@ test_expect_success 'include cycles are detected' '
 	git -C cycle config include.path cycle &&
 	git config -f cycle/cycle include.path config &&
 	test_must_fail \
-		env GIT_TEST_GETTEXT_POISON= \
+		env GIT_TEST_GETTEXT_POISON=false \
 		git -C cycle config --get-all test.value 2>stderr &&
 	grep "exceeded maximum include depth" stderr
 '
diff --git a/t/t7201-co.sh b/t/t7201-co.sh
index 5990299fc9..b696bae5f5 100755
--- a/t/t7201-co.sh
+++ b/t/t7201-co.sh
@@ -249,7 +249,7 @@ test_expect_success 'checkout to detach HEAD (with advice declined)' '
 test_expect_success 'checkout to detach HEAD' '
 	git config advice.detachedHead true &&
 	git checkout -f renamer && git clean -f &&
-	GIT_TEST_GETTEXT_POISON= git checkout renamer^ 2>messages &&
+	GIT_TEST_GETTEXT_POISON=false git checkout renamer^ 2>messages &&
 	grep "HEAD is now at 7329388" messages &&
 	test_line_count -gt 1 messages &&
 	H=$(git rev-parse --verify HEAD) &&
diff --git a/t/t9902-completion.sh b/t/t9902-completion.sh
index 43cf313a1c..75512c3403 100755
--- a/t/t9902-completion.sh
+++ b/t/t9902-completion.sh
@@ -1706,7 +1706,7 @@ test_expect_success 'sourcing the completion script clears cached commands' '
 '
 
 test_expect_success 'sourcing the completion script clears cached merge strategies' '
-	GIT_TEST_GETTEXT_POISON= &&
+	GIT_TEST_GETTEXT_POISON=false &&
 	__git_compute_merge_strategies &&
 	verbose test -n "$__git_merge_strategies" &&
 	. "$GIT_BUILD_DIR/contrib/completion/git-completion.bash" &&
diff --git a/t/test-lib.sh b/t/test-lib.sh
index 4b346467df..ed5d69dfe5 100644
--- a/t/test-lib.sh
+++ b/t/test-lib.sh
@@ -1443,11 +1443,9 @@ then
 	unset GIT_TEST_GETTEXT_POISON_ORIG
 fi
 
-# Can we rely on git's output in the C locale?
-if test -z "$GIT_TEST_GETTEXT_POISON"
-then
-	test_set_prereq C_LOCALE_OUTPUT
-fi
+test_lazy_prereq C_LOCALE_OUTPUT '
+	! git env--helper --type=bool --default=0 --exit-code GIT_TEST_GETTEXT_POISON
+'
 
 if test -z "$GIT_TEST_CHECK_CACHE_TREE"
 then