diff --git a/arch/s390/kernel/early.c b/arch/s390/kernel/early.c
index 3b7e7dddc324..668138ee85d9 100644
--- a/arch/s390/kernel/early.c
+++ b/arch/s390/kernel/early.c
@@ -94,6 +94,7 @@ static noinline __init void create_kernel_nss(void)
 	unsigned int sinitrd_pfn, einitrd_pfn;
 #endif
 	int response;
+	int hlen;
 	size_t len;
 	char *savesys_ptr;
 	char defsys_cmd[DEFSYS_CMD_SIZE];
@@ -124,22 +125,24 @@ static noinline __init void create_kernel_nss(void)
 	end_pfn = PFN_UP(__pa(&_end));
 	min_size = end_pfn << 2;
 
-	sprintf(defsys_cmd, "DEFSYS %s 00000-%.5X EW %.5X-%.5X SR %.5X-%.5X",
-		kernel_nss_name, stext_pfn - 1, stext_pfn, eshared_pfn - 1,
-		eshared_pfn, end_pfn);
+	hlen = snprintf(defsys_cmd, DEFSYS_CMD_SIZE,
+			"DEFSYS %s 00000-%.5X EW %.5X-%.5X SR %.5X-%.5X",
+			kernel_nss_name, stext_pfn - 1, stext_pfn,
+			eshared_pfn - 1, eshared_pfn, end_pfn);
 
 #ifdef CONFIG_BLK_DEV_INITRD
 	if (INITRD_START && INITRD_SIZE) {
 		sinitrd_pfn = PFN_DOWN(__pa(INITRD_START));
 		einitrd_pfn = PFN_UP(__pa(INITRD_START + INITRD_SIZE));
 		min_size = einitrd_pfn << 2;
-		sprintf(defsys_cmd, "%s EW %.5X-%.5X", defsys_cmd,
-		sinitrd_pfn, einitrd_pfn);
+		hlen += snprintf(defsys_cmd + hlen, DEFSYS_CMD_SIZE - hlen,
+				 " EW %.5X-%.5X", sinitrd_pfn, einitrd_pfn);
 	}
 #endif
 
-	sprintf(defsys_cmd, "%s EW MINSIZE=%.7iK PARMREGS=0-13",
-		defsys_cmd, min_size);
+	snprintf(defsys_cmd + hlen, DEFSYS_CMD_SIZE - hlen,
+		 " EW MINSIZE=%.7iK PARMREGS=0-13", min_size);
+	defsys_cmd[DEFSYS_CMD_SIZE - 1] = '\0';
 	sprintf(savesys_cmd, "SAVESYS %s \n IPL %s",
 		kernel_nss_name, kernel_nss_name);