diff --git a/hw/i2c/pmbus_device.c b/hw/i2c/pmbus_device.c
index c3d6046784..44fe4eddbb 100644
--- a/hw/i2c/pmbus_device.c
+++ b/hw/i2c/pmbus_device.c
@@ -94,6 +94,13 @@ void pmbus_send64(PMBusDevice *pmdev, uint64_t data)
 
 void pmbus_send_string(PMBusDevice *pmdev, const char *data)
 {
+    if (!data) {
+        qemu_log_mask(LOG_GUEST_ERROR,
+                      "%s: %s: uninitialised read from 0x%02x\n",
+                      __func__, DEVICE(pmdev)->canonical_path, pmdev->code);
+        return;
+    }
+
     size_t len = strlen(data);
     g_assert(len > 0);
     g_assert(len + pmdev->out_buf_len < SMBUS_DATA_MAX_LEN);