Index: src/checkin.c
==================================================================
--- src/checkin.c
+++ src/checkin.c
@@ -1046,13 +1046,14 @@
   ** array is allocated to contain the "id" field from the vfile table
   ** for each file to be committed. Or, if aCommitFile is NULL, all files
   ** should be committed.
   */
   select_commit_files();
-  isAMerge = db_exists("SELECT 1 FROM vmerge");
+  /* id=0 means that it introduces a new parent */
+  isAMerge = db_exists("SELECT 1 FROM vmerge WHERE id=0");
   if( g.aCommitFile && isAMerge ){
-    fossil_fatal("cannot do a partial commit of a merge");
+    fossil_fatal("cannot do a partial commit of a graph merge");
   }
 
   user_select();
   /*
   ** Check that the user exists.