Index: src/math.c
==================================================================
--- src/math.c
+++ src/math.c
@@ -132,11 +132,11 @@
   xHi = x>>32;
   yHi = y>>32;
   if( xHi*yHi ) return 1;
   xLo = x & 0xffffffff;
   yLo = y & 0xffffffff;
-  if( (xHi*yLo + yHi*xLo)>0xffffffff ) return 1;
+  if( (xHi*yLo + yHi*xLo + (xLo*yLo>>32))>0xffffffff ) return 1;
   return 0;
 }
 
 /*
 ** Multiply two numbers and return the result.

Index: test/num.test
==================================================================
--- test/num.test
+++ test/num.test
@@ -97,10 +97,18 @@
 } { 
   do_test num-5.1.$tn {
     sqlite4_num_to_text [sqlite4_num_mul $a $b]
   } $product
 }
+# 5.2: Overflow that depends on the product of the two least 
+# significant halves
+do_test num-5.2.1 {
+  sqlite4_num_mul 3 6148914691236517211
+} {sign:0 approx:1 e:1 m:1844674407370955163}
+do_test num-5.2.2 {
+  sqlite4_num_mul 3 6148914690091192593
+} {sign:0 approx:0 e:0 m:18446744070273577779}
 
 do_test num-6.1.1 {
   sqlite4_num_to_text [sqlite4_num_div 6 5]
 } {1.2}
 do_test num-6.1.2 {