diff --git a/tools/kwbimage.c b/tools/kwbimage.c
index 5830549..ccecf87 100644
--- a/tools/kwbimage.c
+++ b/tools/kwbimage.c
@@ -290,6 +290,33 @@ static uint8_t image_checksum8(void *start, uint32_t len)
 	return csum;
 }
 
+size_t kwbimage_header_size(unsigned char *ptr)
+{
+	if (image_version((void *)ptr) == 0)
+		return sizeof(struct main_hdr_v0);
+	else
+		return KWBHEADER_V1_SIZE((struct main_hdr_v1 *)ptr);
+}
+
+/*
+ * Verify checksum over a complete header that includes the checksum field.
+ * Return 1 when OK, otherwise 0.
+ */
+static int main_hdr_checksum_ok(void *hdr)
+{
+	/* Offsets of checksum in v0 and v1 headers are the same */
+	struct main_hdr_v0 *main_hdr = (struct main_hdr_v0 *)hdr;
+	uint8_t checksum;
+
+	checksum = image_checksum8(hdr, kwbimage_header_size(hdr));
+	/* Calculated checksum includes the header checksum field. Compensate
+	 * for that.
+	 */
+	checksum -= main_hdr->checksum;
+
+	return checksum == main_hdr->checksum;
+}
+
 static uint32_t image_checksum32(void *start, uint32_t len)
 {
 	uint32_t csum = 0;
@@ -1587,14 +1614,9 @@ static int kwbimage_check_image_types(uint8_t type)
 static int kwbimage_verify_header(unsigned char *ptr, int image_size,
 				  struct image_tool_params *params)
 {
-	struct main_hdr_v0 *main_hdr;
 	uint8_t checksum;
 
-	main_hdr = (struct main_hdr_v0 *)ptr;
-	checksum = image_checksum8(ptr,
-				   sizeof(struct main_hdr_v0)
-				   - sizeof(uint8_t));
-	if (checksum != main_hdr->checksum)
+	if (!main_hdr_checksum_ok(ptr))
 		return -FDT_ERR_BADSTRUCTURE;
 
 	/* Only version 0 extended header has checksum */