diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index 0d92dcd036..7e82ea34f2 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -378,6 +378,8 @@ errstart(int elevel, const char *filename, int lineno,
 	edata->funcname = funcname;
 	/* the default text domain is the backend's */
 	edata->domain = domain ? domain : PG_TEXTDOMAIN("postgres");
+	/* initialize context_domain the same way (see set_errcontext_domain()) */
+	edata->context_domain = edata->domain;
 	/* Select default errcode based on elevel */
 	if (elevel >= ERROR)
 		edata->sqlerrcode = ERRCODE_INTERNAL_ERROR;
@@ -728,7 +730,7 @@ errcode_for_socket_access(void)
 		char		   *fmtbuf; \
 		StringInfoData	buf; \
 		/* Internationalize the error format string */ \
-		if (translateit && !in_error_recursion_trouble()) \
+		if ((translateit) && !in_error_recursion_trouble()) \
 			fmt = dgettext((domain), fmt);				  \
 		/* Expand %m in format string */ \
 		fmtbuf = expand_fmt_string(fmt, edata); \
@@ -1048,6 +1050,16 @@ errcontext_msg(const char *fmt,...)
  * translate it.  Instead, each errcontext_msg() call should be preceded by
  * a set_errcontext_domain() call to specify the domain.  This is usually
  * done transparently by the errcontext() macro.
+ *
+ * Although errcontext is primarily meant for use at call sites distant from
+ * the original ereport call, there are a few places that invoke errcontext
+ * within ereport.  The expansion of errcontext as a comma expression calling
+ * set_errcontext_domain then errcontext_msg is problematic in this case,
+ * because the intended comma expression becomes two arguments to errfinish,
+ * which the compiler is at liberty to evaluate in either order.  But in
+ * such a case, the set_errcontext_domain calls must be selecting the same
+ * TEXTDOMAIN value that the errstart call did, so order does not matter
+ * so long as errstart initializes context_domain along with domain.
  */
 int
 set_errcontext_domain(const char *domain)
@@ -1057,7 +1069,8 @@ set_errcontext_domain(const char *domain)
 	/* we don't bother incrementing recursion_depth */
 	CHECK_STACK_DEPTH();
 
-	edata->context_domain = domain;
+	/* the default text domain is the backend's */
+	edata->context_domain = domain ? domain : PG_TEXTDOMAIN("postgres");
 
 	return 0;					/* return value does not matter */
 }