Index: ext/fts5/fts5_main.c
==================================================================
--- ext/fts5/fts5_main.c
+++ ext/fts5/fts5_main.c
@@ -1495,13 +1495,12 @@
   /* A transaction must be open when this is called. */
   assert( pTab->ts.eState==1 );
 
   assert( pVtab->zErrMsg==0 );
   assert( nArg==1 || nArg==(2+pConfig->nCol+2) );
-  assert( nArg==1 
-      || sqlite3_value_type(apVal[1])==SQLITE_INTEGER 
-      || sqlite3_value_type(apVal[1])==SQLITE_NULL 
+  assert( sqlite3_value_type(apVal[0])==SQLITE_INTEGER 
+       || sqlite3_value_type(apVal[0])==SQLITE_NULL 
   );
   assert( pTab->pConfig->pzErrmsg==0 );
   pTab->pConfig->pzErrmsg = &pTab->base.zErrMsg;
 
   /* Put any active cursors into REQUIRE_SEEK state. */
@@ -1554,45 +1553,51 @@
     else if( nArg==1 ){
       i64 iDel = sqlite3_value_int64(apVal[0]);  /* Rowid to delete */
       rc = sqlite3Fts5StorageDelete(pTab->pStorage, iDel, 0);
     }
 
-    /* INSERT */
-    else if( eType0!=SQLITE_INTEGER ){     
-      /* If this is a REPLACE, first remove the current entry (if any) */
-      if( eConflict==SQLITE_REPLACE 
-       && sqlite3_value_type(apVal[1])==SQLITE_INTEGER 
-      ){
-        i64 iNew = sqlite3_value_int64(apVal[1]);  /* Rowid to delete */
-        rc = sqlite3Fts5StorageDelete(pTab->pStorage, iNew, 0);
-      }
-      fts5StorageInsert(&rc, pTab, apVal, pRowid);
-    }
-
-    /* UPDATE */
-    else{
-      i64 iOld = sqlite3_value_int64(apVal[0]);  /* Old rowid */
-      i64 iNew = sqlite3_value_int64(apVal[1]);  /* New rowid */
-      if( iOld!=iNew ){
-        if( eConflict==SQLITE_REPLACE ){
-          rc = sqlite3Fts5StorageDelete(pTab->pStorage, iOld, 0);
-          if( rc==SQLITE_OK ){
-            rc = sqlite3Fts5StorageDelete(pTab->pStorage, iNew, 0);
-          }
-          fts5StorageInsert(&rc, pTab, apVal, pRowid);
-        }else{
-          rc = sqlite3Fts5StorageContentInsert(pTab->pStorage, apVal, pRowid);
-          if( rc==SQLITE_OK ){
-            rc = sqlite3Fts5StorageDelete(pTab->pStorage, iOld, 0);
-          }
-          if( rc==SQLITE_OK ){
-            rc = sqlite3Fts5StorageIndexInsert(pTab->pStorage, apVal, *pRowid);
-          }
-        }
-      }else{
-        rc = sqlite3Fts5StorageDelete(pTab->pStorage, iOld, 0);
-        fts5StorageInsert(&rc, pTab, apVal, pRowid);
+    /* INSERT or UPDATE */
+    else{
+      int eType1 = sqlite3_value_numeric_type(apVal[1]);
+
+      if( eType1!=SQLITE_INTEGER && eType1!=SQLITE_NULL ){
+        rc = SQLITE_MISMATCH;
+      }
+
+      else if( eType0!=SQLITE_INTEGER ){     
+        /* If this is a REPLACE, first remove the current entry (if any) */
+        if( eConflict==SQLITE_REPLACE && eType1==SQLITE_INTEGER ){
+          i64 iNew = sqlite3_value_int64(apVal[1]);  /* Rowid to delete */
+          rc = sqlite3Fts5StorageDelete(pTab->pStorage, iNew, 0);
+        }
+        fts5StorageInsert(&rc, pTab, apVal, pRowid);
+      }
+
+      /* UPDATE */
+      else{
+        i64 iOld = sqlite3_value_int64(apVal[0]);  /* Old rowid */
+        i64 iNew = sqlite3_value_int64(apVal[1]);  /* New rowid */
+        if( eType1==SQLITE_INTEGER && iOld!=iNew ){
+          if( eConflict==SQLITE_REPLACE ){
+            rc = sqlite3Fts5StorageDelete(pTab->pStorage, iOld, 0);
+            if( rc==SQLITE_OK ){
+              rc = sqlite3Fts5StorageDelete(pTab->pStorage, iNew, 0);
+            }
+            fts5StorageInsert(&rc, pTab, apVal, pRowid);
+          }else{
+            rc = sqlite3Fts5StorageContentInsert(pTab->pStorage, apVal, pRowid);
+            if( rc==SQLITE_OK ){
+              rc = sqlite3Fts5StorageDelete(pTab->pStorage, iOld, 0);
+            }
+            if( rc==SQLITE_OK ){
+              rc = sqlite3Fts5StorageIndexInsert(pTab->pStorage, apVal,*pRowid);
+            }
+          }
+        }else{
+          rc = sqlite3Fts5StorageDelete(pTab->pStorage, iOld, 0);
+          fts5StorageInsert(&rc, pTab, apVal, pRowid);
+        }
       }
     }
   }
 
   pTab->pConfig->pzErrmsg = 0;

Index: ext/fts5/test/fts5update.test
==================================================================
--- ext/fts5/test/fts5update.test
+++ ext/fts5/test/fts5update.test
@@ -132,10 +132,24 @@
       INSERT INTO x3(x3) VALUES('optimize');
     }
   }
 } {}
 
+do_execsql_test 4.0 {
+  CREATE VIRTUAL TABLE x4 USING fts5(a, detail=%DETAIL%);
+  INSERT INTO x4 VALUES('one two three');
+  INSERT INTO x4(rowid, a) VALUES('2', 'one two three');
+  INSERT INTO x4(rowid, a) VALUES('3.0', 'one two three');
+}
+do_catchsql_test 4.1 {
+  INSERT INTO x4(rowid, a) VALUES('four', 'one two three');
+} {1 {datatype mismatch}}
+
+do_catchsql_test 4.2 {
+  UPDATE x4 SET rowid = 'four' WHERE rowid=1;
+} {1 {datatype mismatch}}
+
 
 }
 
 reset_db
 do_catchsql_test 4.0 { CREATE VIRTUAL TABLE t1 USING fts5(a,b,c); } {0 {}}