Index: src/build.c
==================================================================
--- src/build.c
+++ src/build.c
@@ -1952,11 +1952,11 @@
       pParse->nTab = 2;
       addrTop = sqlite3VdbeCurrentAddr(v) + 1;
       sqlite3VdbeAddOp3(v, OP_InitCoroutine, regYield, 0, addrTop);
       sqlite3SelectDestInit(&dest, SRT_Coroutine, regYield);
       sqlite3Select(pParse, pSelect, &dest);
-      sqlite3VdbeAddOp1(v, OP_EndCoroutine, regYield);
+      sqlite3VdbeEndCoroutine(v, regYield);
       sqlite3VdbeJumpHere(v, addrTop - 1);
       if( pParse->nErr ) return;
       pSelTab = sqlite3ResultSetOfSelect(pParse, pSelect);
       if( pSelTab==0 ) return;
       assert( p->aCol==0 );

Index: src/insert.c
==================================================================
--- src/insert.c
+++ src/insert.c
@@ -683,11 +683,11 @@
     dest.iSdst = bIdListInOrder ? regData : 0;
     dest.nSdst = pTab->nCol;
     rc = sqlite3Select(pParse, pSelect, &dest);
     regFromSelect = dest.iSdst;
     if( rc || db->mallocFailed || pParse->nErr ) goto insert_cleanup;
-    sqlite3VdbeAddOp1(v, OP_EndCoroutine, regYield);
+    sqlite3VdbeEndCoroutine(v, regYield);
     sqlite3VdbeJumpHere(v, addrTop - 1);                       /* label B: */
     assert( pSelect->pEList );
     nColumn = pSelect->pEList->nExpr;
 
     /* Set useTempTable to TRUE if the result of the SELECT statement

Index: src/select.c
==================================================================
--- src/select.c
+++ src/select.c
@@ -2950,11 +2950,11 @@
   addr1 = sqlite3VdbeAddOp3(v, OP_InitCoroutine, regAddrA, 0, addrSelectA);
   VdbeComment((v, "left SELECT"));
   pPrior->iLimit = regLimitA;
   explainSetInteger(iSub1, pParse->iNextSelectId);
   sqlite3Select(pParse, pPrior, &destA);
-  sqlite3VdbeAddOp1(v, OP_EndCoroutine, regAddrA);
+  sqlite3VdbeEndCoroutine(v, regAddrA);
   sqlite3VdbeJumpHere(v, addr1);
 
   /* Generate a coroutine to evaluate the SELECT statement on 
   ** the right - the "B" select
   */
@@ -2967,11 +2967,11 @@
   p->iOffset = 0;  
   explainSetInteger(iSub2, pParse->iNextSelectId);
   sqlite3Select(pParse, p, &destB);
   p->iLimit = savedLimit;
   p->iOffset = savedOffset;
-  sqlite3VdbeAddOp1(v, OP_EndCoroutine, regAddrB);
+  sqlite3VdbeEndCoroutine(v, regAddrB);
 
   /* Generate a subroutine that outputs the current row of the A
   ** select as the next output row of the compound select.
   */
   VdbeNoopComment((v, "Output routine for A"));
@@ -4988,11 +4988,11 @@
       explainSetInteger(pItem->iSelectId, (u8)pParse->iNextSelectId);
       sqlite3Select(pParse, pSub, &dest);
       pItem->pTab->nRowLogEst = sqlite3LogEst(pSub->nSelectRow);
       pItem->fg.viaCoroutine = 1;
       pItem->regResult = dest.iSdst;
-      sqlite3VdbeAddOp1(v, OP_EndCoroutine, pItem->regReturn);
+      sqlite3VdbeEndCoroutine(v, pItem->regReturn);
       sqlite3VdbeJumpHere(v, addrTop-1);
       sqlite3ClearTempRegCache(pParse);
     }else{
       /* Generate a subroutine that will fill an ephemeral table with
       ** the content of this subquery.  pItem->addrFillSub will point

Index: src/vdbe.h
==================================================================
--- src/vdbe.h
+++ src/vdbe.h
@@ -178,10 +178,11 @@
 void sqlite3VdbeMultiLoad(Vdbe*,int,const char*,...);
 int sqlite3VdbeAddOp3(Vdbe*,int,int,int,int);
 int sqlite3VdbeAddOp4(Vdbe*,int,int,int,int,const char *zP4,int);
 int sqlite3VdbeAddOp4Dup8(Vdbe*,int,int,int,int,const u8*,int);
 int sqlite3VdbeAddOp4Int(Vdbe*,int,int,int,int,int);
+void sqlite3VdbeEndCoroutine(Vdbe*,int);
 #if defined(SQLITE_DEBUG) && !defined(SQLITE_TEST_REALLOC_STRESS)
   void sqlite3VdbeVerifyNoMallocRequired(Vdbe *p, int N);
 #else
 # define sqlite3VdbeVerifyNoMallocRequired(A,B)
 #endif

Index: src/vdbeaux.c
==================================================================
--- src/vdbeaux.c
+++ src/vdbeaux.c
@@ -321,10 +321,25 @@
 ){
   int addr = sqlite3VdbeAddOp3(p, op, p1, p2, p3);
   sqlite3VdbeChangeP4(p, addr, SQLITE_INT_TO_PTR(p4), P4_INT32);
   return addr;
 }
+
+/* Insert the end of a co-routine
+*/
+void sqlite3VdbeEndCoroutine(Vdbe *v, int regYield){
+  sqlite3VdbeAddOp1(v, OP_EndCoroutine, regYield);
+
+  /* Clear the temporary register cache, thereby ensuring that each
+  ** co-routine has its own independent set of registers, because co-routines
+  ** might expect their registers to be preserved across an OP_Yield, and
+  ** that could cause problems if two or more co-routines are using the same
+  ** temporary register.
+  */
+  v->pParse->nTempReg = 0;
+  v->pParse->nRangeReg = 0;
+}
 
 /*
 ** Create a new symbolic label for an instruction that has yet to be
 ** coded.  The symbolic label is really just a negative number.  The
 ** label can be used as the P2 value of an operation.  Later, when

Index: test/select4.test
==================================================================
--- test/select4.test
+++ test/select4.test
@@ -913,7 +913,27 @@
   VALUES(1),(2),(3),(4) UNION ALL SELECT 5 LIMIT 99;
 } {1 2 3 4 5}
 do_execsql_test select4-14.17 {
   VALUES(1),(2),(3),(4) UNION ALL SELECT 5 LIMIT 3;
 } {1 2 3}
+
+# Ticket https://www.sqlite.org/src/info/d06a25c84454a372
+# Incorrect answer due to two co-routines using the same registers and expecting
+# those register values to be preserved across a Yield.
+#
+do_execsql_test select4-15.1 {
+  DROP TABLE IF EXISTS tx;
+  CREATE TABLE tx(id INTEGER PRIMARY KEY, a, b);
+  INSERT INTO tx(a,b) VALUES(33,456);
+  INSERT INTO tx(a,b) VALUES(33,789);
+
+  SELECT DISTINCT t0.id, t0.a, t0.b
+    FROM tx AS t0, tx AS t1
+   WHERE t0.a=t1.a AND t1.a=33 AND t0.b=456
+  UNION
+  SELECT DISTINCT t0.id, t0.a, t0.b
+    FROM tx AS t0, tx AS t1
+   WHERE t0.a=t1.a AND t1.a=33 AND t0.b=789
+   ORDER BY 1;
+} {1 33 456 2 33 789}
 
 finish_test