diff --git a/Makefile b/Makefile
index 8b0433a6..a30fac65 100644
--- a/Makefile
+++ b/Makefile
@@ -245,6 +245,9 @@ test32: xxhsum32
 TEST_FILES = xxhsum$(EXT) xxhash.c xxhash.h
 .PHONY: test-xxhsum-c
 test-xxhsum-c: xxhsum
+	# --seed requires a value
+	./xxhsum --seed 2>&1 | $(GREP) -q "^Wrong parameters"
+	./xxhsum -H0 --seed 2>&1 | $(GREP) -q "^Wrong parameters"
 	# xxhsum to/from pipe
 	./xxhsum $(TEST_FILES) | ./xxhsum -c -
 	./xxhsum -H0 $(TEST_FILES) | ./xxhsum -c -
diff --git a/cli/xxhsum.c b/cli/xxhsum.c
index f8e43c08..154e7577 100644
--- a/cli/xxhsum.c
+++ b/cli/xxhsum.c
@@ -1615,6 +1615,7 @@ XSUM_API int XSUM_main(int argc, const char* argv[])
         if (!strcmp(argument, "--seed") ){
             const char* seed_str;
             i++;
+            if (i >= argc) return XSUM_badusage(exename);
             seed_str = argv[i];
             switch( algo ){
                     case algo_xxh32  : g_default_seed_u32 = XSUM_readU32FromChar(&seed_str); break;