diff --git a/src/interfaces/ecpg/ecpglib/misc.c b/src/interfaces/ecpg/ecpglib/misc.c
index 6778c45883..40785640b1 100644
--- a/src/interfaces/ecpg/ecpglib/misc.c
+++ b/src/interfaces/ecpg/ecpglib/misc.c
@@ -513,13 +513,14 @@ char *
 ecpg_gettext(const char *msgid)
 {
 	/*
-	 * If multiple threads come through here at about the same time, it's okay
-	 * for more than one of them to call bindtextdomain().  But it's not okay
-	 * for any of them to reach dgettext() before bindtextdomain() is
-	 * complete, so don't set the flag till that's done.  Use "volatile" just
-	 * to be sure the compiler doesn't try to get cute.
+	 * At least on Windows, there are gettext implementations that fail if
+	 * multiple threads call bindtextdomain() concurrently.  Use a mutex and
+	 * flag variable to ensure that we call it just once per process.  It is
+	 * not known that similar bugs exist on non-Windows platforms, but we
+	 * might as well do it the same way everywhere.
 	 */
 	static volatile bool already_bound = false;
+	static pthread_mutex_t binddomain_mutex = PTHREAD_MUTEX_INITIALIZER;
 
 	if (!already_bound)
 	{
@@ -529,14 +530,26 @@ ecpg_gettext(const char *msgid)
 #else
 		int			save_errno = errno;
 #endif
-		const char *ldir;
 
-		/* No relocatable lookup here because the binary could be anywhere */
-		ldir = getenv("PGLOCALEDIR");
-		if (!ldir)
-			ldir = LOCALEDIR;
-		bindtextdomain(PG_TEXTDOMAIN("ecpglib"), ldir);
-		already_bound = true;
+		(void) pthread_mutex_lock(&binddomain_mutex);
+
+		if (!already_bound)
+		{
+			const char *ldir;
+
+			/*
+			 * No relocatable lookup here because the calling executable could
+			 * be anywhere
+			 */
+			ldir = getenv("PGLOCALEDIR");
+			if (!ldir)
+				ldir = LOCALEDIR;
+			bindtextdomain(PG_TEXTDOMAIN("ecpglib"), ldir);
+			already_bound = true;
+		}
+
+		(void) pthread_mutex_unlock(&binddomain_mutex);
+
 #ifdef WIN32
 		SetLastError(save_errno);
 #else
diff --git a/src/interfaces/libpq/fe-misc.c b/src/interfaces/libpq/fe-misc.c
index 1664410c51..724f1693ee 100644
--- a/src/interfaces/libpq/fe-misc.c
+++ b/src/interfaces/libpq/fe-misc.c
@@ -1272,13 +1272,14 @@ static void
 libpq_binddomain(void)
 {
 	/*
-	 * If multiple threads come through here at about the same time, it's okay
-	 * for more than one of them to call bindtextdomain().  But it's not okay
-	 * for any of them to return to caller before bindtextdomain() is
-	 * complete, so don't set the flag till that's done.  Use "volatile" just
-	 * to be sure the compiler doesn't try to get cute.
+	 * At least on Windows, there are gettext implementations that fail if
+	 * multiple threads call bindtextdomain() concurrently.  Use a mutex and
+	 * flag variable to ensure that we call it just once per process.  It is
+	 * not known that similar bugs exist on non-Windows platforms, but we
+	 * might as well do it the same way everywhere.
 	 */
 	static volatile bool already_bound = false;
+	static pthread_mutex_t binddomain_mutex = PTHREAD_MUTEX_INITIALIZER;
 
 	if (!already_bound)
 	{
@@ -1288,14 +1289,26 @@ libpq_binddomain(void)
 #else
 		int			save_errno = errno;
 #endif
-		const char *ldir;
 
-		/* No relocatable lookup here because the binary could be anywhere */
-		ldir = getenv("PGLOCALEDIR");
-		if (!ldir)
-			ldir = LOCALEDIR;
-		bindtextdomain(PG_TEXTDOMAIN("libpq"), ldir);
-		already_bound = true;
+		(void) pthread_mutex_lock(&binddomain_mutex);
+
+		if (!already_bound)
+		{
+			const char *ldir;
+
+			/*
+			 * No relocatable lookup here because the calling executable could
+			 * be anywhere
+			 */
+			ldir = getenv("PGLOCALEDIR");
+			if (!ldir)
+				ldir = LOCALEDIR;
+			bindtextdomain(PG_TEXTDOMAIN("libpq"), ldir);
+			already_bound = true;
+		}
+
+		(void) pthread_mutex_unlock(&binddomain_mutex);
+
 #ifdef WIN32
 		SetLastError(save_errno);
 #else