diff --git a/Makefile b/Makefile
index c153f450c5..c348bb7337 100644
--- a/Makefile
+++ b/Makefile
@@ -216,6 +216,9 @@ all::
 #
 # Define NO_REGEX if you have no or inferior regex support in your C library.
 #
+# Define GETTEXT_POISON if you are debugging the choice of strings marked
+# for translation.  This will turn all strings that use gettext into gibberish.
+#
 # Define JSMIN to point to JavaScript minifier that functions as
 # a filter to have gitweb.js minified.
 #
@@ -1370,6 +1373,9 @@ endif
 ifdef NO_SYMLINK_HEAD
 	BASIC_CFLAGS += -DNO_SYMLINK_HEAD
 endif
+ifdef GETTEXT_POISON
+	BASIC_CFLAGS += -DGETTEXT_POISON
+endif
 ifdef NO_STRCASESTR
 	COMPAT_CFLAGS += -DNO_STRCASESTR
 	COMPAT_OBJS += compat/strcasestr.o
@@ -2089,6 +2095,7 @@ endif
 ifdef GIT_TEST_CMP_USE_COPIED_CONTEXT
 	@echo GIT_TEST_CMP_USE_COPIED_CONTEXT=YesPlease >>$@
 endif
+	@echo GETTEXT_POISON=\''$(subst ','\'',$(subst ','\'',$(GETTEXT_POISON)))'\' >>$@
 
 ### Detect Tck/Tk interpreter path changes
 ifndef NO_TCLTK
diff --git a/gettext.h b/gettext.h
index 6949d736d5..11d82b0a6e 100644
--- a/gettext.h
+++ b/gettext.h
@@ -15,9 +15,15 @@
 
 #define FORMAT_PRESERVING(n) __attribute__((format_arg(n)))
 
+#ifdef GETTEXT_POISON
+#define use_gettext_poison() 1
+#else
+#define use_gettext_poison() 0
+#endif
+
 static inline FORMAT_PRESERVING(1) const char *_(const char *msgid)
 {
-	return msgid;
+	return use_gettext_poison() ? "# GETTEXT POISON #" : msgid;
 }
 
 /* Mark msgid for translation but do not translate it. */
diff --git a/t/test-lib.sh b/t/test-lib.sh
index 0fdc541a7c..0840e4a5c9 100644
--- a/t/test-lib.sh
+++ b/t/test-lib.sh
@@ -1079,6 +1079,9 @@ esac
 test -z "$NO_PERL" && test_set_prereq PERL
 test -z "$NO_PYTHON" && test_set_prereq PYTHON
 
+# Can we rely on git's output in the C locale?
+test -z "$GETTEXT_POISON" && test_set_prereq C_LOCALE_OUTPUT
+
 # test whether the filesystem supports symbolic links
 ln -s x y 2>/dev/null && test -h y 2>/dev/null && test_set_prereq SYMLINKS
 rm -f y