diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index e950b41374b..49eec3e8356 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -6739,6 +6739,14 @@ PQerrorMessage(const PGconn *conn)
 	if (!conn)
 		return libpq_gettext("connection pointer is NULL\n");
 
+	/*
+	 * The errorMessage buffer might be marked "broken" due to having
+	 * previously failed to allocate enough memory for the message.  In that
+	 * case, tell the application we ran out of memory.
+	 */
+	if (PQExpBufferBroken(&conn->errorMessage))
+		return libpq_gettext("out of memory\n");
+
 	return conn->errorMessage.data;
 }
 
diff --git a/src/interfaces/libpq/fe-exec.c b/src/interfaces/libpq/fe-exec.c
index aca81890bb1..6c7b3df0127 100644
--- a/src/interfaces/libpq/fe-exec.c
+++ b/src/interfaces/libpq/fe-exec.c
@@ -191,7 +191,7 @@ PQmakeEmptyPGresult(PGconn *conn, ExecStatusType status)
 				/* non-error cases */
 				break;
 			default:
-				pqSetResultError(result, conn->errorMessage.data);
+				pqSetResultError(result, &conn->errorMessage);
 				break;
 		}
 
@@ -662,14 +662,28 @@ pqResultStrdup(PGresult *res, const char *str)
  *		assign a new error message to a PGresult
  */
 void
-pqSetResultError(PGresult *res, const char *msg)
+pqSetResultError(PGresult *res, PQExpBuffer errorMessage)
 {
+	char	   *msg;
+
 	if (!res)
 		return;
-	if (msg && *msg)
-		res->errMsg = pqResultStrdup(res, msg);
+
+	/*
+	 * We handle two OOM scenarios here.  The errorMessage buffer might be
+	 * marked "broken" due to having previously failed to allocate enough
+	 * memory for the message, or it might be fine but pqResultStrdup fails
+	 * and returns NULL.  In either case, just make res->errMsg point directly
+	 * at a constant "out of memory" string.
+	 */
+	if (!PQExpBufferBroken(errorMessage))
+		msg = pqResultStrdup(res, errorMessage->data);
 	else
-		res->errMsg = NULL;
+		msg = NULL;
+	if (msg)
+		res->errMsg = msg;
+	else
+		res->errMsg = libpq_gettext("out of memory\n");
 }
 
 /*
@@ -852,19 +866,19 @@ pqInternalNotice(const PGNoticeHooks *hooks, const char *fmt,...)
 	/* XXX should provide a SQLSTATE too? */
 
 	/*
-	 * Result text is always just the primary message + newline. If we can't
-	 * allocate it, don't bother invoking the receiver.
+	 * Result text is always just the primary message + newline.  If we can't
+	 * allocate it, substitute "out of memory", as in pqSetResultError.
 	 */
 	res->errMsg = (char *) pqResultAlloc(res, strlen(msgBuf) + 2, false);
 	if (res->errMsg)
-	{
 		sprintf(res->errMsg, "%s\n", msgBuf);
+	else
+		res->errMsg = libpq_gettext("out of memory\n");
 
-		/*
-		 * Pass to receiver, then free it.
-		 */
-		res->noticeHooks.noticeRec(res->noticeHooks.noticeRecArg, res);
-	}
+	/*
+	 * Pass to receiver, then free it.
+	 */
+	res->noticeHooks.noticeRec(res->noticeHooks.noticeRecArg, res);
 	PQclear(res);
 }
 
@@ -2122,7 +2136,7 @@ PQgetResult(PGconn *conn)
 				appendPQExpBuffer(&conn->errorMessage,
 								  libpq_gettext("PGEventProc \"%s\" failed during PGEVT_RESULTCREATE event\n"),
 								  res->events[i].name);
-				pqSetResultError(res, conn->errorMessage.data);
+				pqSetResultError(res, &conn->errorMessage);
 				res->resultStatus = PGRES_FATAL_ERROR;
 				break;
 			}
diff --git a/src/interfaces/libpq/fe-protocol3.c b/src/interfaces/libpq/fe-protocol3.c
index 2e833053487..9ab3bf1fcb6 100644
--- a/src/interfaces/libpq/fe-protocol3.c
+++ b/src/interfaces/libpq/fe-protocol3.c
@@ -967,12 +967,12 @@ pqGetErrorNotice3(PGconn *conn, bool isError)
 	if (isError)
 	{
 		if (res)
-			res->errMsg = pqResultStrdup(res, workBuf.data);
+			pqSetResultError(res, &workBuf);
 		pqClearAsyncResult(conn);	/* redundant, but be safe */
 		conn->result = res;
 		if (PQExpBufferDataBroken(workBuf))
 			appendPQExpBufferStr(&conn->errorMessage,
-								 libpq_gettext("out of memory"));
+								 libpq_gettext("out of memory\n"));
 		else
 			appendPQExpBufferStr(&conn->errorMessage, workBuf.data);
 	}
@@ -981,8 +981,15 @@ pqGetErrorNotice3(PGconn *conn, bool isError)
 		/* if we couldn't allocate the result set, just discard the NOTICE */
 		if (res)
 		{
-			/* We can cheat a little here and not copy the message. */
-			res->errMsg = workBuf.data;
+			/*
+			 * We can cheat a little here and not copy the message.  But if we
+			 * were unlucky enough to run out of memory while filling workBuf,
+			 * insert "out of memory", as in pqSetResultError.
+			 */
+			if (PQExpBufferDataBroken(workBuf))
+				res->errMsg = libpq_gettext("out of memory\n");
+			else
+				res->errMsg = workBuf.data;
 			if (res->noticeHooks.noticeRec != NULL)
 				res->noticeHooks.noticeRec(res->noticeHooks.noticeRecArg, res);
 			PQclear(res);
diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h
index e9f214b61b9..490458adef5 100644
--- a/src/interfaces/libpq/libpq-int.h
+++ b/src/interfaces/libpq/libpq-int.h
@@ -637,7 +637,7 @@ extern pgthreadlock_t pg_g_threadlock;
 
 /* === in fe-exec.c === */
 
-extern void pqSetResultError(PGresult *res, const char *msg);
+extern void pqSetResultError(PGresult *res, PQExpBuffer errorMessage);
 extern void *pqResultAlloc(PGresult *res, size_t nBytes, bool isBinary);
 extern char *pqResultStrdup(PGresult *res, const char *str);
 extern void pqClearAsyncResult(PGconn *conn);