Index: ext/icu/icu.c
==================================================================
--- ext/icu/icu.c
+++ ext/icu/icu.c
@@ -347,11 +347,11 @@
 ** of the locale to use. Passing an empty string ("") or SQL NULL value
 ** as the second argument is the same as invoking the 1 argument version
 ** of upper() or lower().
 **
 **     lower('I', 'en_us') -> 'i'
-**     lower('I', 'tr_tr') -> 'ı' (small dotless i)
+**     lower('I', 'tr_tr') -> '\u131' (small dotless i)
 **
 ** http://www.icu-project.org/userguide/posix.html#case_mappings
 */
 static void icuCaseFunc16(sqlite3_context *p, int nArg, sqlite3_value **apArg){
   const UChar *zInput;            /* Pointer to input string */

Index: src/mutex.h
==================================================================
--- src/mutex.h
+++ src/mutex.h
@@ -48,10 +48,17 @@
 #  else
 #    define SQLITE_MUTEX_NOOP
 #  endif
 #endif
 
+/*
+** Allowed values for sqlite3_mutex.magic
+*/
+#define SQLITE_MUTEXMAGIC_NORMAL  0x1f7a8074
+#define SQLITE_MUTEXMAGIC_TRACE   0x1f7a8075
+#define SQLITE_MUTEXMAGIC_DEAD    0x4b0844f6
+
 #ifdef SQLITE_MUTEX_OMIT
 /*
 ** If this is a no-op implementation, implement everything as macros.
 */
 #define sqlite3_mutex_alloc(X)    ((sqlite3_mutex*)8)

Index: src/mutex_w32.c
==================================================================
--- src/mutex_w32.c
+++ src/mutex_w32.c
@@ -38,11 +38,11 @@
   CRITICAL_SECTION mutex;    /* Mutex controlling the lock */
   int id;                    /* Mutex type */
 #ifdef SQLITE_DEBUG
   volatile int nRef;         /* Number of enterances */
   volatile DWORD owner;      /* Thread holding this mutex */
-  volatile int trace;        /* True to trace changes */
+  volatile u32 magic;        /* True to trace changes */
 #endif
 };
 
 /*
 ** These are the initializer values used when declaring a "static" mutex
@@ -219,11 +219,13 @@
       p = sqlite3MallocZero( sizeof(*p) );
       if( p ){
         p->id = iType;
 #ifdef SQLITE_DEBUG
 #ifdef SQLITE_WIN32_MUTEX_TRACE_DYNAMIC
-        p->trace = 1;
+        p->magic = SQLITE_MUTEXMAGIC_TRACE;
+#else
+        p->magic = SQLITE_MUTEXMAGIC_NORMAL;
 #endif
 #endif
 #if SQLITE_OS_WINRT
         InitializeCriticalSectionEx(&p->mutex, 0, 0);
 #else
@@ -241,11 +243,13 @@
 #endif
       p = &winMutex_staticMutexes[iType-2];
       p->id = iType;
 #ifdef SQLITE_DEBUG
 #ifdef SQLITE_WIN32_MUTEX_TRACE_STATIC
-      p->trace = 1;
+      p->magic = SQLITE_MUTEXMAGIC_TRACE;
+#else
+      p->magic = SQLITE_MUTEXMAGIC_NORMAL;
 #endif
 #endif
       break;
     }
   }
@@ -258,10 +262,11 @@
 ** allocated mutex.  SQLite is careful to deallocate every
 ** mutex that it allocates.
 */
 static void winMutexFree(sqlite3_mutex *p){
   assert( p );
+  assert( (p->magic&~1)==SQLITE_MUTEXMAGIC_NORMAL );
   assert( p->nRef==0 && p->owner==0 );
   if( p->id==SQLITE_MUTEX_FAST || p->id==SQLITE_MUTEX_RECURSIVE ){
     DeleteCriticalSection(&p->mutex);
     sqlite3_free(p);
   }else{
@@ -284,25 +289,24 @@
 */
 static void winMutexEnter(sqlite3_mutex *p){
 #if defined(SQLITE_DEBUG) || defined(SQLITE_TEST)
   DWORD tid = GetCurrentThreadId();
 #endif
-#ifdef SQLITE_DEBUG
   assert( p );
+  assert( (p->magic&~1)==SQLITE_MUTEXMAGIC_NORMAL );
+#ifdef SQLITE_DEBUG
   assert( p->id==SQLITE_MUTEX_RECURSIVE || winMutexNotheld2(p, tid) );
-#else
-  assert( p );
 #endif
   assert( winMutex_isInit==1 );
   EnterCriticalSection(&p->mutex);
 #ifdef SQLITE_DEBUG
   assert( p->nRef>0 || p->owner==0 );
   p->owner = tid;
   p->nRef++;
-  if( p->trace ){
-    OSTRACE(("ENTER-MUTEX tid=%lu, mutex=%p (%d), nRef=%d\n",
-             tid, p, p->trace, p->nRef));
+  if( p->magic&1 ){
+    OSTRACE(("ENTER-MUTEX tid=%lu, mutex=%p (%lu), nRef=%d\n",
+             tid, p, p->magic, p->nRef));
   }
 #endif
 }
 
 static int winMutexTry(sqlite3_mutex *p){
@@ -309,11 +313,14 @@
 #if defined(SQLITE_DEBUG) || defined(SQLITE_TEST)
   DWORD tid = GetCurrentThreadId();
 #endif
   int rc = SQLITE_BUSY;
   assert( p );
+  assert( (p->magic&~1)==SQLITE_MUTEXMAGIC_NORMAL );
+#ifdef SQLITE_DEBUG
   assert( p->id==SQLITE_MUTEX_RECURSIVE || winMutexNotheld2(p, tid) );
+#endif
   /*
   ** The sqlite3_mutex_try() routine is very rarely used, and when it
   ** is used it is merely an optimization.  So it is OK for it to always
   ** fail.
   **
@@ -339,13 +346,13 @@
   }
 #else
   UNUSED_PARAMETER(p);
 #endif
 #ifdef SQLITE_DEBUG
-  if( p->trace ){
-    OSTRACE(("TRY-MUTEX tid=%lu, mutex=%p (%d), owner=%lu, nRef=%d, rc=%s\n",
-             tid, p, p->trace, p->owner, p->nRef, sqlite3ErrName(rc)));
+  if( p->magic&1 ){
+    OSTRACE(("TRY-MUTEX tid=%lu, mutex=%p (%lu), owner=%lu, nRef=%d, rc=%s\n",
+             tid, p, p->magic, p->owner, p->nRef, sqlite3ErrName(rc)));
   }
 #endif
   return rc;
 }
 
@@ -358,10 +365,11 @@
 static void winMutexLeave(sqlite3_mutex *p){
 #if defined(SQLITE_DEBUG) || defined(SQLITE_TEST)
   DWORD tid = GetCurrentThreadId();
 #endif
   assert( p );
+  assert( (p->magic&~1)==SQLITE_MUTEXMAGIC_NORMAL );
 #ifdef SQLITE_DEBUG
   assert( p->nRef>0 );
   assert( p->owner==tid );
   p->nRef--;
   if( p->nRef==0 ) p->owner = 0;
@@ -368,13 +376,13 @@
   assert( p->nRef==0 || p->id==SQLITE_MUTEX_RECURSIVE );
 #endif
   assert( winMutex_isInit==1 );
   LeaveCriticalSection(&p->mutex);
 #ifdef SQLITE_DEBUG
-  if( p->trace ){
-    OSTRACE(("LEAVE-MUTEX tid=%lu, mutex=%p (%d), nRef=%d\n",
-             tid, p, p->trace, p->nRef));
+  if( p->magic&1 ){
+    OSTRACE(("LEAVE-MUTEX tid=%lu, mutex=%p (%lu), nRef=%d\n",
+             tid, p, p->magic, p->nRef));
   }
 #endif
 }
 
 sqlite3_mutex_methods const *sqlite3DefaultMutex(void){