diff --git a/src/backend/utils/init/miscinit.c b/src/backend/utils/init/miscinit.c
index 865119d272..f590ecb25e 100644
--- a/src/backend/utils/init/miscinit.c
+++ b/src/backend/utils/init/miscinit.c
@@ -325,6 +325,14 @@ InitStandaloneProcess(const char *argv0)
 
 	MyStartTime = time(NULL);	/* set our start time in case we call elog */
 
+	/*
+	 * Initialize random() for the first time, like PostmasterMain() would.
+	 * In a regular IsUnderPostmaster backend, BackendRun() computes a
+	 * high-entropy seed before any user query.  Fewer distinct initial seeds
+	 * can occur here.
+	 */
+	srandom((unsigned int) (MyProcPid ^ MyStartTime));
+
 	/* Initialize process-local latch support */
 	InitializeLatchSupport();
 	MyLatch = &LocalLatchData;
diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.c
index cb8c7450d9..e155c6ae2f 100644
--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -923,6 +923,9 @@ choose_dsm_implementation(void)
 #ifdef HAVE_SHM_OPEN
 	int			ntries = 10;
 
+	/* Initialize random(); this function is its only user in this program. */
+	srandom((unsigned int) (getpid() ^ time(NULL)));
+
 	while (ntries > 0)
 	{
 		uint32		handle;