Index: src/pcache.c
==================================================================
--- src/pcache.c
+++ src/pcache.c
@@ -650,11 +650,11 @@
 int sqlite3PcacheSetSpillsize(PCache *p, int mxPage){
   int res;
   assert( p->pCache!=0 );
   if( mxPage ){
     if( mxPage<0 ){
-      mxPage = (int)((-1024*(i64)p->szCache)/(p->szPage+p->szExtra));
+      mxPage = (int)((-1024*(i64)mxPage)/(p->szPage+p->szExtra));
     }
     p->szSpill = mxPage;
   }
   res = numberOfCachePages(p);
   if( res<p->szSpill ) res = p->szSpill; 

Index: src/pragma.c
==================================================================
--- src/pragma.c
+++ src/pragma.c
@@ -767,26 +767,27 @@
   **
   ** The cache_spill=BOOLEAN setting applies to all attached schemas,
   ** not just the schema specified.
   */
   case PragTyp_CACHE_SPILL: {
-    int size;
     assert( sqlite3SchemaMutexHeld(db, iDb, 0) );
     if( !zRight ){
       if( sqlite3ReadSchema(pParse) ) goto pragma_out;
       returnSingleInt(v, "cache_spill", 
          (db->flags & SQLITE_CacheSpill)==0 ? 0 : 
             sqlite3BtreeSetSpillSize(pDb->pBt,0));
     }else{
+      int size = 1;
       if( sqlite3GetInt32(zRight, &size) ){
         sqlite3BtreeSetSpillSize(pDb->pBt, size);
       }
-      if( sqlite3GetBoolean(zRight, 0) ){
+      if( sqlite3GetBoolean(zRight, size!=0) ){
         db->flags |= SQLITE_CacheSpill;
       }else{
         db->flags &= ~SQLITE_CacheSpill;
       }
+      setAllPagerFlags(db);
     }
     break;
   }
 
   /*

Index: test/pragma2.test
==================================================================
--- test/pragma2.test
+++ test/pragma2.test
@@ -195,20 +195,31 @@
     PRAGMA cache_spill;
     BEGIN;
     UPDATE t1 SET c=c+1;
     PRAGMA lock_status;
   }
-} {100000 main reserved temp unknown}   ;# Large cache spill threshold
+} {100000 main reserved temp unknown}   ;# Big spill threshold -> no excl lock
 do_test pragma2-4.5.3 {
   db eval {
     ROLLBACK;
     PRAGMA cache_spill=25;
+    PRAGMA main.cache_spill;
+    BEGIN;
+    UPDATE t1 SET c=c+1;
+    PRAGMA lock_status;
+  }
+} {50 main exclusive temp unknown}   ;# Small cache spill -> exclusive lock
+do_test pragma2-4.5.4 {
+  db eval {
+    ROLLBACK;
+    PRAGMA cache_spill(-25);
+    PRAGMA main.cache_spill;
     BEGIN;
     UPDATE t1 SET c=c+1;
     PRAGMA lock_status;
   }
-} {main exclusive temp unknown}   ;# Large cache spill, so no exclusive lock
+} {50 main exclusive temp unknown}   ;# Small cache spill -> exclusive lock
 
 
 # Verify that newly attached databases inherit the cache_spill=OFF
 # setting.
 #
@@ -229,8 +240,28 @@
   PRAGMA cache_spill=ON; -- Applies to all databases
   BEGIN;
   UPDATE t2 SET c=c-1;
   PRAGMA lock_status;
 } {main unlocked temp unknown aux1 exclusive}
+db close
+forcedelete test.db
+sqlite3 db test.db
+
+breakpoint
+do_execsql_test pragma2-5.1 {
+  PRAGMA page_size=16384;
+  CREATE TABLE t1(x);
+  PRAGMA cache_size=2;
+  PRAGMA cache_spill=YES;
+  PRAGMA cache_spill;
+} {2}
+do_execsql_test pragma2-5.2 {
+  PRAGMA cache_spill=NO;
+  PRAGMA cache_spill;
+} {0}
+do_execsql_test pragma2-5.3 {
+  PRAGMA cache_spill(-51);
+  PRAGMA cache_spill;
+} {3}
    
 test_restore_config_pagecache
 finish_test