diff --git a/libisofs/ecma119.c b/libisofs/ecma119.c
index 22a6882..fb44cbb 100644
--- a/libisofs/ecma119.c
+++ b/libisofs/ecma119.c
@@ -896,20 +896,24 @@ int checksum_prepare_image(IsoImage *src, int flag)
   @flag bit0= recursion
 */
 static
-int checksum_prepare_nodes(IsoImage *img, IsoNode *node, int flag)
+int checksum_prepare_nodes(Ecma119Image *target, IsoNode *node, int flag)
 {
     IsoNode *pos;
     IsoFile *file;
-    int ret, i;
+    IsoImage *img;
+    int ret, i, no_md5 = 0;
     size_t value_length;
     unsigned int idx = 0;
     char *value;
     void *xipt = NULL;
 
+    img= target->image;
+
     if (node->type == LIBISO_FILE) {
         file = (IsoFile *) node;
-        if (file->from_old_session) {
-            /* Save eventual MD5 data of files from old image */
+        if (file->from_old_session && target->appendable) {
+            /* Save MD5 data of files from old image which will not
+               be copied and have an MD5 recorded in the old image. */
             value= NULL;
             ret = iso_node_lookup_attr(node, "isofs.cx", &value_length,
                                        &value, 0);
@@ -924,18 +928,25 @@ int checksum_prepare_nodes(IsoImage *img, IsoNode *node, int flag)
                                              xipt);
                     if (ret < 0)
                         return ret;
-                }
+                } else
+                    no_md5 = 1;
+            } else {
+                no_md5 = 1;
             }
             if (value != NULL)
                 free(value);
         }
-        /* Equip all nodes with provisory isofs.cx numbers: 4 byte, all 0. */
-        ret = iso_file_set_isofscx(file, (unsigned int) 0, 0);
-        if (ret < 0)
-            return ret;
+        /* Equip nodes with provisory isofs.cx numbers: 4 byte, all 0.
+           Omit those from old image which will not be copied and have no MD5.
+         */
+        if (!no_md5) {
+            ret = iso_file_set_isofscx(file, (unsigned int) 0, 0);
+            if (ret < 0)
+                return ret;
+        }
     } else if (node->type == LIBISO_DIR) {
         for (pos = ((IsoDir *) node)->children; pos != NULL; pos = pos->next) {
-            ret = checksum_prepare_nodes(img, pos, 1);
+            ret = checksum_prepare_nodes(target, pos, 1);
             if (ret < 0)
                 return ret;
         }
@@ -1081,7 +1092,7 @@ int ecma119_image_new(IsoImage *src, IsoWriteOpts *opts, Ecma119Image **img)
         if (ret < 0)
             return ret;
         if (target->appendable) {
-            ret = checksum_prepare_nodes(src, (IsoNode *) src->root, 0);
+            ret = checksum_prepare_nodes(target, (IsoNode *) src->root, 0);
             if (ret < 0)
                 return ret;
         }
diff --git a/libisofs/filesrc.c b/libisofs/filesrc.c
index 6a4c22b..206bec0 100644
--- a/libisofs/filesrc.c
+++ b/libisofs/filesrc.c
@@ -49,7 +49,8 @@ int iso_file_src_create(Ecma119Image *img, IsoFile *file, IsoFileSrc **src)
     ino_t ino_id;
 
 #ifdef Libisofs_with_checksumS
-    int cret;
+    int cret, no_md5= 0;
+    void *xipt = NULL;
 #endif
 
     if (img == NULL || file == NULL || src == NULL) {
@@ -99,7 +100,7 @@ int iso_file_src_create(Ecma119Image *img, IsoFile *file, IsoFileSrc **src)
 
 #ifdef Libisofs_with_checksumS
 
-        if (ret == 0) {
+        if (ret == 0 && (*src)->checksum_index > 0) {
             /* Duplicate file source was mapped to previously registered source
             */
             cret = iso_file_set_isofscx(file, (*src)->checksum_index, 0);
@@ -117,7 +118,14 @@ int iso_file_src_create(Ecma119Image *img, IsoFile *file, IsoFileSrc **src)
 
 #ifdef Libisofs_with_checksumS
 
-    if(img->md5_file_checksums) {
+    if (img->md5_file_checksums && file->from_old_session && img->appendable) {
+        /* Omit MD5 indexing with old image nodes which have no MD5 */
+        ret = iso_node_get_xinfo((IsoNode *) file, checksum_xinfo_func, &xipt);
+        if (ret <= 0)
+            no_md5 = 1;
+    }
+
+    if (img->md5_file_checksums && !no_md5) {
         img->checksum_idx_counter++;
         if (img->checksum_idx_counter < 0x80000000) {
             fsrc->checksum_index= img->checksum_idx_counter;
diff --git a/libisofs/libisofs.h b/libisofs/libisofs.h
index 7b644ba..025fd4c 100644
--- a/libisofs/libisofs.h
+++ b/libisofs/libisofs.h
@@ -5033,7 +5033,8 @@ int iso_image_get_session_md5(IsoImage *image, uint32_t *start_lba,
  * @param md5
  *      Eventually returns 16 byte of MD5 checksum 
  * @param flag
- *      Bitfield for control purposes, unused yet, submit 0
+ *      Bitfield for control purposes
+ *      bit0= only determine return value, do not touch parameter md5
  * @return
  *      1= md5 found , 0= no md5 available , <0 indicates error
  *
diff --git a/libisofs/md5.c b/libisofs/md5.c
index ad405d2..b9b4313 100644
--- a/libisofs/md5.c
+++ b/libisofs/md5.c
@@ -427,7 +427,7 @@ int checksum_copy_old_nodes(Ecma119Image *target, IsoNode *node, int flag)
 
     if (node->type == LIBISO_FILE) {
         file = (IsoFile *) node;
-        if (file->from_old_session) {
+        if (file->from_old_session && target->appendable) {
             ret = iso_node_get_xinfo(node, checksum_xinfo_func, &xipt);
             if (ret <= 0)
                 return ret;
diff --git a/libisofs/node.c b/libisofs/node.c
index 008ab5e..7b55b7d 100644
--- a/libisofs/node.c
+++ b/libisofs/node.c
@@ -2696,8 +2696,11 @@ int iso_file_get_md5(IsoImage *image, IsoFile *file, char md5[16], int flag)
         ret = 0;
         goto ex;
     }
-    memcpy(md5, image->checksum_array + ((size_t) 16) * ((size_t) idx), 16);
-    ret = ISO_SUCCESS;
+    if (!(flag & 1)) {
+        memcpy(md5, image->checksum_array + ((size_t) 16) * ((size_t) idx),
+               16);
+    }
+    ret = 1;
 ex:;
     if (value != NULL)
         free(value);