diff --git a/.travis.yml b/.travis.yml
index 8d2499739e..a329a0add6 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -24,7 +24,7 @@ addons:
 
 matrix:
   include:
-    - env: jobname=GETTEXT_POISON
+    - env: jobname=GIT_TEST_GETTEXT_POISON
       os: linux
       compiler:
       addons:
diff --git a/Makefile b/Makefile
index bbfbb4292d..f3a9995e50 100644
--- a/Makefile
+++ b/Makefile
@@ -362,11 +362,6 @@ all::
 # Define HAVE_DEV_TTY if your system can open /dev/tty to interact with the
 # user.
 #
-# Define GETTEXT_POISON if you are debugging the choice of strings marked
-# for translation.  In a GETTEXT_POISON build, you can turn all strings marked
-# for translation into gibberish by setting the GIT_GETTEXT_POISON variable
-# (to any value) in your environment.
-#
 # Define JSMIN to point to JavaScript minifier that functions as
 # a filter to have gitweb.js minified.
 #
@@ -1452,7 +1447,7 @@ ifdef NO_SYMLINK_HEAD
 	BASIC_CFLAGS += -DNO_SYMLINK_HEAD
 endif
 ifdef GETTEXT_POISON
-	BASIC_CFLAGS += -DGETTEXT_POISON
+$(error The GETTEXT_POISON option has been removed in favor of runtime GIT_TEST_GETTEXT_POISON. See t/README!)
 endif
 ifdef NO_GETTEXT
 	BASIC_CFLAGS += -DNO_GETTEXT
@@ -2603,7 +2598,6 @@ ifdef GIT_TEST_CMP_USE_COPIED_CONTEXT
 	@echo GIT_TEST_CMP_USE_COPIED_CONTEXT=YesPlease >>$@+
 endif
 	@echo NO_GETTEXT=\''$(subst ','\'',$(subst ','\'',$(NO_GETTEXT)))'\' >>$@+
-	@echo GETTEXT_POISON=\''$(subst ','\'',$(subst ','\'',$(GETTEXT_POISON)))'\' >>$@+
 ifdef GIT_PERF_REPEAT_COUNT
 	@echo GIT_PERF_REPEAT_COUNT=\''$(subst ','\'',$(subst ','\'',$(GIT_PERF_REPEAT_COUNT)))'\' >>$@+
 endif
diff --git a/ci/lib-travisci.sh b/ci/lib-travisci.sh
index 06970f7213..69dff4d1ec 100755
--- a/ci/lib-travisci.sh
+++ b/ci/lib-travisci.sh
@@ -123,7 +123,7 @@ osx-clang|osx-gcc)
 	# Travis CI OS X
 	export GIT_SKIP_TESTS="t9810 t9816"
 	;;
-GETTEXT_POISON)
-	export GETTEXT_POISON=YesPlease
+GIT_TEST_GETTEXT_POISON)
+	export GIT_TEST_GETTEXT_POISON=YesPlease
 	;;
 esac
diff --git a/gettext.c b/gettext.c
index 7272771c8e..d4021d690c 100644
--- a/gettext.c
+++ b/gettext.c
@@ -7,6 +7,7 @@
 #include "gettext.h"
 #include "strbuf.h"
 #include "utf8.h"
+#include "config.h"
 
 #ifndef NO_GETTEXT
 #	include <locale.h>
@@ -46,15 +47,15 @@ const char *get_preferred_languages(void)
 	return NULL;
 }
 
-#ifdef GETTEXT_POISON
 int use_gettext_poison(void)
 {
 	static int poison_requested = -1;
-	if (poison_requested == -1)
-		poison_requested = getenv("GIT_GETTEXT_POISON") ? 1 : 0;
+	if (poison_requested == -1) {
+		const char *v = getenv("GIT_TEST_GETTEXT_POISON");
+		poison_requested = v && strlen(v) ? 1 : 0;
+	}
 	return poison_requested;
 }
-#endif
 
 #ifndef NO_GETTEXT
 static int test_vsnprintf(const char *fmt, ...)
@@ -164,6 +165,8 @@ void git_setup_gettext(void)
 	if (!podir)
 		podir = p = system_path(GIT_LOCALE_PATH);
 
+	use_gettext_poison(); /* getenv() reentrancy paranoia */
+
 	if (!is_directory(podir)) {
 		free(p);
 		return;
diff --git a/gettext.h b/gettext.h
index 7eee64a34f..71255e503e 100644
--- a/gettext.h
+++ b/gettext.h
@@ -28,12 +28,15 @@
 
 #define FORMAT_PRESERVING(n) __attribute__((format_arg(n)))
 
+extern int use_gettext_poison(void);
+
 #ifndef NO_GETTEXT
 extern void git_setup_gettext(void);
 extern int gettext_width(const char *s);
 #else
 static inline void git_setup_gettext(void)
 {
+	use_gettext_poison(); /* getenv() reentrancy paranoia */
 }
 static inline int gettext_width(const char *s)
 {
@@ -41,12 +44,6 @@ static inline int gettext_width(const char *s)
 }
 #endif
 
-#ifdef GETTEXT_POISON
-extern int use_gettext_poison(void);
-#else
-#define use_gettext_poison() 0
-#endif
-
 static inline FORMAT_PRESERVING(1) const char *_(const char *msgid)
 {
 	if (!*msgid)
diff --git a/git-sh-i18n.sh b/git-sh-i18n.sh
index 9d065fb4bf..e1d917fd27 100644
--- a/git-sh-i18n.sh
+++ b/git-sh-i18n.sh
@@ -17,7 +17,7 @@ export TEXTDOMAINDIR
 
 # First decide what scheme to use...
 GIT_INTERNAL_GETTEXT_SH_SCHEME=fallthrough
-if test -n "$GIT_GETTEXT_POISON"
+if test -n "$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 fef4c0f0b5..aa704ffcb7 100644
--- a/po/README
+++ b/po/README
@@ -289,16 +289,11 @@ something in the test suite might still depend on the US English
 version of the strings, e.g. to grep some error message or other
 output.
 
-To smoke out issues like these Git can be compiled with gettext poison
-support, at the top-level:
+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.:
 
-    make GETTEXT_POISON=YesPlease
-
-That'll give you a git which emits gibberish on every call to
-gettext. It's obviously not meant to be installed, but you should run
-the test suite with it:
-
-    cd t && prove -j 9 ./t[0-9]*.sh
+    cd t && GIT_TEST_GETTEXT_POISON=YesPlease 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 2e9bef2852..bb2db49615 100644
--- a/t/README
+++ b/t/README
@@ -302,6 +302,12 @@ that cannot be easily covered by a few specific test cases. These
 could be enabled by running the test suite with correct GIT_TEST_
 environment set.
 
+GIT_TEST_GETTEXT_POISON=<non-empty?> turns all strings marked for
+translation into gibberish if non-empty (think "test -n"). 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.
+
 GIT_TEST_SPLIT_INDEX=<boolean> forces split-index mode on the whole
 test suite. Accept any boolean values that are accepted by git-config.
 
diff --git a/t/lib-gettext.sh b/t/lib-gettext.sh
index eec757f104..755f421431 100644
--- a/t/lib-gettext.sh
+++ b/t/lib-gettext.sh
@@ -12,7 +12,7 @@ export GIT_TEXTDOMAINDIR GIT_PO_PATH
 
 . "$GIT_BUILD_DIR"/git-sh-i18n
 
-if test_have_prereq GETTEXT && ! test_have_prereq GETTEXT_POISON
+if test_have_prereq GETTEXT && test_have_prereq C_LOCALE_OUTPUT
 then
 	# is_IS.UTF-8 on Solaris and FreeBSD, is_IS.utf8 on Debian
 	is_IS_locale=$(locale -a 2>/dev/null |
diff --git a/t/t0000-basic.sh b/t/t0000-basic.sh
index 4d23373526..b6566003dd 100755
--- a/t/t0000-basic.sh
+++ b/t/t0000-basic.sh
@@ -274,7 +274,7 @@ test_expect_success 'pretend we have a mix of all possible results' "
 	EOF
 "
 
-test_expect_success 'test --verbose' '
+test_expect_success C_LOCALE_OUTPUT 'test --verbose' '
 	test_must_fail run_sub_test_lib_test \
 		test-verbose "test verbose" --verbose <<-\EOF &&
 	test_expect_success "passing test" true
diff --git a/t/t0205-gettext-poison.sh b/t/t0205-gettext-poison.sh
index 438e778d6a..a06269f38a 100755
--- a/t/t0205-gettext-poison.sh
+++ b/t/t0205-gettext-poison.sh
@@ -5,13 +5,15 @@
 
 test_description='Gettext Shell poison'
 
+GIT_TEST_GETTEXT_POISON=YesPlease
+export GIT_TEST_GETTEXT_POISON
 . ./lib-gettext.sh
 
-test_expect_success GETTEXT_POISON 'sanity: $GIT_INTERNAL_GETTEXT_SH_SCHEME" is poison' '
+test_expect_success 'sanity: $GIT_INTERNAL_GETTEXT_SH_SCHEME" is poison' '
     test "$GIT_INTERNAL_GETTEXT_SH_SCHEME" = "poison"
 '
 
-test_expect_success GETTEXT_POISON 'gettext: our gettext() fallback has poison semantics' '
+test_expect_success 'gettext: our gettext() fallback has poison semantics' '
     printf "# GETTEXT POISON #" >expect &&
     gettext "test" >actual &&
     test_cmp expect actual &&
@@ -20,7 +22,7 @@ test_expect_success GETTEXT_POISON 'gettext: our gettext() fallback has poison s
     test_cmp expect actual
 '
 
-test_expect_success GETTEXT_POISON 'eval_gettext: our eval_gettext() fallback has poison semantics' '
+test_expect_success 'eval_gettext: our eval_gettext() fallback has poison semantics' '
     printf "# GETTEXT POISON #" >expect &&
     eval_gettext "test" >actual &&
     test_cmp expect actual &&
diff --git a/t/t3406-rebase-message.sh b/t/t3406-rebase-message.sh
index 0392e36d23..2bdcf83808 100755
--- a/t/t3406-rebase-message.sh
+++ b/t/t3406-rebase-message.sh
@@ -77,7 +77,7 @@ test_expect_success 'rebase -n overrides config rebase.stat config' '
 #     "Does not point to a valid commit: invalid-ref"
 #
 # NEEDSWORK: This "grep" is fine in real non-C locales, but
-# GETTEXT_POISON poisons the refname along with the enclosing
+# GIT_TEST_GETTEXT_POISON poisons the refname along with the enclosing
 # error message.
 test_expect_success 'rebase --onto outputs the invalid ref' '
 	test_must_fail git rebase --onto invalid-ref HEAD HEAD 2>err &&
diff --git a/t/t7201-co.sh b/t/t7201-co.sh
index 826987ca80..72b9b375ba 100755
--- a/t/t7201-co.sh
+++ b/t/t7201-co.sh
@@ -254,9 +254,9 @@ 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 checkout renamer^ 2>messages &&
-	test_i18ngrep "HEAD is now at 7329388" messages &&
-	(test_line_count -gt 1 messages || test -n "$GETTEXT_POISON") &&
+	GIT_TEST_GETTEXT_POISON= git checkout renamer^ 2>messages &&
+	grep "HEAD is now at 7329388" messages &&
+	test_line_count -gt 1 messages &&
 	H=$(git rev-parse --verify HEAD) &&
 	M=$(git show-ref -s --verify refs/heads/master) &&
 	test "z$H" = "z$M" &&
diff --git a/t/t9902-completion.sh b/t/t9902-completion.sh
index 175f83d704..3c6b185b60 100755
--- a/t/t9902-completion.sh
+++ b/t/t9902-completion.sh
@@ -1697,7 +1697,8 @@ test_expect_success 'sourcing the completion script clears cached commands' '
 	verbose test -z "$__git_all_commands"
 '
 
-test_expect_success !GETTEXT_POISON 'sourcing the completion script clears cached merge strategies' '
+test_expect_success 'sourcing the completion script clears cached merge strategies' '
+	GIT_TEST_GETTEXT_POISON= &&
 	__git_compute_merge_strategies &&
 	verbose test -n "$__git_merge_strategies" &&
 	. "$GIT_BUILD_DIR/contrib/completion/git-completion.bash" &&
diff --git a/t/test-lib-functions.sh b/t/test-lib-functions.sh
index 78d8c3783b..2f42b3653c 100644
--- a/t/test-lib-functions.sh
+++ b/t/test-lib-functions.sh
@@ -755,16 +755,16 @@ test_cmp_bin() {
 
 # Use this instead of test_cmp to compare files that contain expected and
 # actual output from git commands that can be translated.  When running
-# under GETTEXT_POISON this pretends that the command produced expected
+# under GIT_TEST_GETTEXT_POISON this pretends that the command produced expected
 # results.
 test_i18ncmp () {
-	test -n "$GETTEXT_POISON" || test_cmp "$@"
+	! test_have_prereq C_LOCALE_OUTPUT || test_cmp "$@"
 }
 
 # Use this instead of "grep expected-string actual" to see if the
 # output from a git command that can be translated either contains an
 # expected string, or does not contain an unwanted one.  When running
-# under GETTEXT_POISON this pretends that the command produced expected
+# under GIT_TEST_GETTEXT_POISON this pretends that the command produced expected
 # results.
 test_i18ngrep () {
 	eval "last_arg=\${$#}"
@@ -779,7 +779,7 @@ test_i18ngrep () {
 		error "bug in the test script: too few parameters to test_i18ngrep"
 	fi
 
-	if test -n "$GETTEXT_POISON"
+	if test_have_prereq !C_LOCALE_OUTPUT
 	then
 		# pretend success
 		return 0
diff --git a/t/test-lib.sh b/t/test-lib.sh
index 47a99aa0ed..b50f934dcd 100644
--- a/t/test-lib.sh
+++ b/t/test-lib.sh
@@ -95,6 +95,16 @@ PAGER=cat
 TZ=UTC
 export LANG LC_ALL PAGER TZ
 EDITOR=:
+
+# GIT_TEST_GETTEXT_POISON should not influence git commands executed
+# during initialization of test-lib and the test repo. Back it up,
+# unset and then restore after initialization is finished.
+if test -n "$GIT_TEST_GETTEXT_POISON"
+then
+	GIT_TEST_GETTEXT_POISON_ORIG=$GIT_TEST_GETTEXT_POISON
+	unset GIT_TEST_GETTEXT_POISON
+fi
+
 # A call to "unset" with no arguments causes at least Solaris 10
 # /usr/xpg4/bin/sh and /bin/ksh to bail out.  So keep the unsets
 # deriving from the command substitution clustered with the other
@@ -1104,13 +1114,15 @@ test -n "$USE_LIBPCRE1" && test_set_prereq LIBPCRE1
 test -n "$USE_LIBPCRE2" && test_set_prereq LIBPCRE2
 test -z "$NO_GETTEXT" && test_set_prereq GETTEXT
 
+if test -n "$GIT_TEST_GETTEXT_POISON_ORIG"
+then
+	GIT_TEST_GETTEXT_POISON=$GIT_TEST_GETTEXT_POISON_ORIG
+	unset GIT_TEST_GETTEXT_POISON_ORIG
+fi
+
 # Can we rely on git's output in the C locale?
-if test -n "$GETTEXT_POISON"
+if test -z "$GIT_TEST_GETTEXT_POISON"
 then
-	GIT_GETTEXT_POISON=YesPlease
-	export GIT_GETTEXT_POISON
-	test_set_prereq GETTEXT_POISON
-else
 	test_set_prereq C_LOCALE_OUTPUT
 fi
 
