Index: src/wal.c
==================================================================
--- src/wal.c
+++ src/wal.c
@@ -2898,15 +2898,14 @@
         u32 iZero;
 
         rc = walHashGet(pWal, iHash, &aHash, &aPgno, &iZero);
         if( rc==SQLITE_OK ){
           u32 i, iMin, iMax;
-          assert( iFirst >= iZero );
-          iMin = (iFirst - iZero);
+          assert( head.mxFrame>=iZero );
+          iMin = (iZero >= iFirst) ? 1 : (iFirst - iZero);
           iMax = (iHash==0) ? HASHTABLE_NPAGE_ONE : HASHTABLE_NPAGE;
-          if( iMin<1 ) iMin = 1;
-          if( iMax>head.mxFrame ) iMax = head.mxFrame;
+          if( iMax>(head.mxFrame-iZero) ) iMax = (head.mxFrame-iZero);
           for(i=iMin; rc==SQLITE_OK && i<=iMax; i++){
             PgHdr *pPg;
             if( aPgno[i]==1 ){
               /* Check that the schema cookie has not been modified. If
               ** it has not, the commit can proceed. */

Index: test/concurrent.test
==================================================================
--- test/concurrent.test
+++ test/concurrent.test
@@ -554,8 +554,67 @@
   } {}
 
   do_test 6.$tn.2 {
     list [catch { sql2 { COMMIT } } msg] $msg
   } {1 {database is locked}}
+}
+
+do_multiclient_test tn {
+  do_test 7.$tn.1 {
+    sql1 {
+      PRAGMA journal_mode = wal;
+      CREATE TABLE t1(a INTEGER PRIMARY KEY, b);
+      WITH s(i) AS ( VALUES(1) UNION ALL SELECT i+1 FROM s WHERE i<100) 
+      INSERT INTO t1 SELECT NULL, randomblob(400) FROM s;
+
+      CREATE TABLE t2(a INTEGER PRIMARY KEY, b);
+      WITH s(i) AS ( VALUES(1) UNION ALL SELECT i+1 FROM s WHERE i<50000) 
+      INSERT INTO t2 SELECT NULL, randomblob(400) FROM s;
+
+      CREATE TABLE t3(a INTEGER PRIMARY KEY, b);
+      WITH s(i) AS ( VALUES(1) UNION ALL SELECT i+1 FROM s WHERE i<100) 
+      INSERT INTO t3 SELECT NULL, randomblob(400) FROM s;
+
+      CREATE TABLE t4(a INTEGER PRIMARY KEY, b);
+
+      PRAGMA wal_checkpoint;
+    }
+    set {} {}
+  } {}
+
+  do_test 7.$tn.2 {
+    sql2 {
+      BEGIN CONCURRENT;
+        SELECT * FROM t1;
+        INSERT INTO t4 VALUES(1, 2);
+    }
+    set {} {}
+  } {}
+
+  do_test 7.$tn.3 {
+    sql3 {
+      BEGIN CONCURRENT;
+        SELECT * FROM t3;
+        INSERT INTO t4 VALUES(1, 2);
+    }
+    set {} {}
+  } {}
+
+  do_test 7.$tn.4 {
+    sql1 {
+      UPDATE t1 SET b=randomblob(400);
+      UPDATE t2 SET b=randomblob(400);
+      UPDATE t3 SET b=randomblob(400);
+    }
+  } {}
+
+  do_test 7.$tn.5 {
+    csql2 { COMMIT } 
+  } {1 {database is locked}}
+
+  do_test 7.$tn.6 {
+    csql3 { COMMIT } 
+  } {1 {database is locked}}
+
 }
 
 finish_test