diff --git a/ext/rtree/rtree.c b/ext/rtree/rtree.c
index d6cdde9fc4..66da481e0f 100644
--- a/ext/rtree/rtree.c
+++ b/ext/rtree/rtree.c
@@ -2739,6 +2739,36 @@ static int rtreeDeleteRowid(Rtree *pRtree, sqlite3_int64 iDelete){
   return rc;
 }
 
+/*
+** Rounding constants for float->double conversion.
+*/
+#define RNDTOWARDS  (1.0 - 1.0/8388608.0)  /* Round towards zero */
+#define RNDAWAY     (1.0 + 1.0/8388608.0)  /* Round away from zero */
+
+#if !defined(SQLITE_RTREE_INT_ONLY)
+/*
+** Convert an sqlite3_value into an RtreeValue (presumably a float)
+** while taking care to round toward negative or positive, respectively.
+*/
+static RtreeValue rtreeValueDown(sqlite3_value *v){
+  double d = sqlite3_value_double(v);
+  float f = (float)d;
+  if( f>d ){
+    f = (float)(d*(d<0 ? RNDAWAY : RNDTOWARDS));
+  }
+  return f;
+}
+static RtreeValue rtreeValueUp(sqlite3_value *v){
+  double d = sqlite3_value_double(v);
+  float f = (float)d;
+  if( f<d ){
+    f = (float)(d*(d<0 ? RNDTOWARDS : RNDAWAY));
+  }
+  return f;
+}
+#endif /* !defined(SQLITE_RTREE_INT_ONLY) */
+
+
 /*
 ** The xUpdate method for rtree module virtual tables.
 */
@@ -2775,8 +2805,8 @@ static int rtreeUpdate(
 #ifndef SQLITE_RTREE_INT_ONLY
     if( pRtree->eCoordType==RTREE_COORD_REAL32 ){
       for(ii=0; ii<(pRtree->nDim*2); ii+=2){
-        cell.aCoord[ii].f = (RtreeValue)sqlite3_value_double(azData[ii+3]);
-        cell.aCoord[ii+1].f = (RtreeValue)sqlite3_value_double(azData[ii+4]);
+        cell.aCoord[ii].f = rtreeValueDown(azData[ii+3]);
+        cell.aCoord[ii+1].f = rtreeValueUp(azData[ii+4]);
         if( cell.aCoord[ii].f>cell.aCoord[ii+1].f ){
           rc = SQLITE_CONSTRAINT;
           goto constraint;
diff --git a/manifest b/manifest
index 45aa8d1235..97ff035bc2 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Fix\sthe\sMSVC\smakefile\sso\sthat\sit\sworks\swith\sthe\sunicode61\stokenizer.
-D 2012-05-28T20:22:16.462
+C In\sthe\sRTree\smodule,\smake\ssure\sall\sdouble-to-float\sconversions\sround\sin\sa\ndirection\sto\sincrease\sthe\ssize\sof\selement\sbounding\sboxes.
+D 2012-05-29T00:39:50.223
 F Makefile.arm-wince-mingw32ce-gcc d6df77f1f48d690bd73162294bbba7f59507c72f
 F Makefile.in 4f37eb61be9d38643cdd839a74b8e3bad724cfcf
 F Makefile.linux-gcc 91d710bdc4998cb015f39edf3cb314ec4f4d7e23
@@ -83,7 +83,7 @@ F ext/icu/README.txt bf8461d8cdc6b8f514c080e4e10dc3b2bbdfefa9
 F ext/icu/icu.c eb9ae1d79046bd7871aa97ee6da51eb770134b5a
 F ext/icu/sqliteicu.h 728867a802baa5a96de7495e9689a8e01715ef37
 F ext/rtree/README 6315c0d73ebf0ec40dedb5aa0e942bc8b54e3761
-F ext/rtree/rtree.c 73502e5336162fdc8f5d1c4bdd4ec6b1299c2f2a
+F ext/rtree/rtree.c d17aecb7a92762efa7b1f5d5fd7c88fd77d70827
 F ext/rtree/rtree.h 834dbcb82dc85b2481cde6a07cdadfddc99e9b9e
 F ext/rtree/rtree1.test e474a2b5eff231496dbd073fe67e5fbaf7f444c9
 F ext/rtree/rtree2.test acbb3a4ce0f4fbc2c304d2b4b784cfa161856bba
@@ -1004,7 +1004,7 @@ F tool/tostr.awk e75472c2f98dd76e06b8c9c1367f4ab07e122d06
 F tool/vdbe-compress.tcl d70ea6d8a19e3571d7ab8c9b75cba86d1173ff0f
 F tool/warnings-clang.sh a8a0a3babda96dfb1ff51adda3cbbf3dfb7266c2
 F tool/warnings.sh fbc018d67fd7395f440c28f33ef0f94420226381
-P bcc72d413e8db5fe8b32147ac22d406e2cd6bb60
-R 3124713b2110812cfce2d07ccce3e9e9
+P 480158143be1256cbe4dba52ef1a5b96e172b38c f607ad27c1ede27af24dbee10ca867c8f7761ee3
+R 38bedd0c37f624ccf215394e11ad9336
 U drh
-Z e96acf301cc5f997fc3e1f3cdf1b6355
+Z 4bf39e44bbbf20a271c4dc152544fd6f
diff --git a/manifest.uuid b/manifest.uuid
index 21667c7867..942005486b 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-480158143be1256cbe4dba52ef1a5b96e172b38c
\ No newline at end of file
+0abdc2903d8b3f86cad426e1bac2a959d1b1f7dd
\ No newline at end of file