diff --git a/hw/block/pflash_cfi01.c b/hw/block/pflash_cfi01.c
index 0cbc2fb4cb..9c235bf66e 100644
--- a/hw/block/pflash_cfi01.c
+++ b/hw/block/pflash_cfi01.c
@@ -690,7 +690,7 @@ static const MemoryRegionOps pflash_cfi01_ops = {
     .endianness = DEVICE_NATIVE_ENDIAN,
 };
 
-static void pflash_cfi01_fill_cfi_table(PFlashCFI01 *pfl)
+static void pflash_cfi01_fill_cfi_table(PFlashCFI01 *pfl, Error **errp)
 {
     uint64_t blocks_per_device, sector_len_per_device, device_len;
     int num_devices;
@@ -708,6 +708,10 @@ static void pflash_cfi01_fill_cfi_table(PFlashCFI01 *pfl)
         sector_len_per_device = pfl->sector_len / num_devices;
     }
     device_len = sector_len_per_device * blocks_per_device;
+    if (!is_power_of_2(device_len)) {
+        error_setg(errp, "Device size must be a power of two.");
+        return;
+    }
 
     /* Hardcoded CFI table */
     /* Standard "QRY" string */
@@ -865,7 +869,7 @@ static void pflash_cfi01_realize(DeviceState *dev, Error **errp)
      */
     pfl->cmd = 0x00;
     pfl->status = 0x80; /* WSM ready */
-    pflash_cfi01_fill_cfi_table(pfl);
+    pflash_cfi01_fill_cfi_table(pfl, errp);
 }
 
 static void pflash_cfi01_system_reset(DeviceState *dev)
diff --git a/hw/block/pflash_cfi02.c b/hw/block/pflash_cfi02.c
index 2a99b286b0..ff2fe154c1 100644
--- a/hw/block/pflash_cfi02.c
+++ b/hw/block/pflash_cfi02.c
@@ -880,6 +880,11 @@ static void pflash_cfi02_realize(DeviceState *dev, Error **errp)
         return;
     }
 
+    if (!is_power_of_2(pfl->chip_len)) {
+        error_setg(errp, "Device size must be a power of two.");
+        return;
+    }
+
     memory_region_init_rom_device(&pfl->orig_mem, OBJECT(pfl),
                                   &pflash_cfi02_ops, pfl, pfl->name,
                                   pfl->chip_len, errp);