diff --git a/arch/s390/boot/mem_detect.c b/arch/s390/boot/mem_detect.c
index 0a5821ef4f1f..41792a3a5e36 100644
--- a/arch/s390/boot/mem_detect.c
+++ b/arch/s390/boot/mem_detect.c
@@ -176,7 +176,7 @@ unsigned long detect_memory(void)
 
 	if (!diag260()) {
 		mem_detect.info_source = MEM_DETECT_DIAG260;
-		return max_physmem_end;
+		return max_physmem_end ?: get_mem_detect_end();
 	}
 
 	if (max_physmem_end) {