diff --git a/src/bin/pgbench/pgbench.c b/src/bin/pgbench/pgbench.c
index 9eaa192239..255717bfd2 100644
--- a/src/bin/pgbench/pgbench.c
+++ b/src/bin/pgbench/pgbench.c
@@ -4742,16 +4742,19 @@ set_random_seed(const char *seed)
 	}
 	else
 	{
-		/* parse seed unsigned int value */
+		/* parse unsigned-int seed value */
+		unsigned long ulseed;
 		char		garbage;
 
-		if (sscanf(seed, UINT64_FORMAT "%c", &iseed, &garbage) != 1)
+		/* Don't try to use UINT64_FORMAT here; it might not work for sscanf */
+		if (sscanf(seed, "%lu%c", &ulseed, &garbage) != 1)
 		{
 			fprintf(stderr,
 					"unrecognized random seed option \"%s\": expecting an unsigned integer, \"time\" or \"rand\"\n",
 					seed);
 			return false;
 		}
+		iseed = (uint64) ulseed;
 	}
 
 	if (seed != NULL)