diff --git a/index.html b/index.html
index 6909d1cb..a818a90b 100644
--- a/index.html
+++ b/index.html
@@ -7857,7 +7857,7 @@
     <script src="config/precreated-heightmaps.js"></script>
     <script src="modules/heightmap-generator.js?v=1.88.00"></script>
     <script src="modules/ocean-layers.js?v=1.89.08"></script>
-    <script src="modules/river-generator.js"></script>
+    <script src="modules/river-generator.js?v=1.89.13"></script>
     <script src="modules/lakes.js"></script>
     <script src="modules/names-generator.js?v=1.87.14"></script>
     <script src="modules/cultures-generator.js?v=1.89.10"></script>
@@ -7883,7 +7883,7 @@
     <script defer src="modules/relief-icons.js"></script>
     <script defer src="modules/ui/style.js"></script>
     <script defer src="modules/ui/editors.js?v=1.89.12"></script>
-    <script defer src="modules/ui/tools.js?v=1.89.00"></script>
+    <script defer src="modules/ui/tools.js?v=1.89.13"></script>
     <script defer src="modules/ui/world-configurator.js"></script>
     <script defer src="modules/ui/heightmap-editor.js?v=1.89.06"></script>
     <script defer src="modules/ui/provinces-editor.js?v=1.89.00"></script>
@@ -7897,7 +7897,7 @@
     <script defer src="modules/ui/coastline-editor.js"></script>
     <script defer src="modules/ui/labels-editor.js"></script>
     <script defer src="modules/ui/rivers-editor.js"></script>
-    <script defer src="modules/ui/rivers-creator.js"></script>
+    <script defer src="modules/ui/rivers-creator.js?v=1.89.13"></script>
     <script defer src="modules/ui/relief-editor.js"></script>
     <script defer src="modules/ui/burg-editor.js"></script>
     <script defer src="modules/ui/units-editor.js"></script>
diff --git a/modules/river-generator.js b/modules/river-generator.js
index 957fe6fc..fd8a95b4 100644
--- a/modules/river-generator.js
+++ b/modules/river-generator.js
@@ -48,7 +48,9 @@ window.Rivers = (function () {
         cells.fl[i] += prec[cells.g[i]] / cellsNumberModifier; // add flux from precipitation
 
         // create lake outlet if lake is not in deep depression and flux > evaporation
-        const lakes = lakeOutCells[i] ? features.filter(feature => i === feature.outCell && feature.flux > feature.evaporation) : [];
+        const lakes = lakeOutCells[i]
+          ? features.filter(feature => i === feature.outCell && feature.flux > feature.evaporation)
+          : [];
         for (const lake of lakes) {
           const lakeCell = cells.c[i].find(c => h[c] < 20 && cells.f[c] === lake.i);
           cells.fl[lakeCell] += Math.max(lake.flux - lake.evaporation, 0); // not evaporated lake water drains to outlet
@@ -191,7 +193,18 @@ window.Rivers = (function () {
         const length = getApproximateLength(meanderedPoints);
         const width = getWidth(getOffset(discharge, meanderedPoints.length, widthFactor, 0));
 
-        pack.rivers.push({i: riverId, source, mouth, discharge, length, width, widthFactor, sourceWidth: 0, parent, cells: riverCells});
+        pack.rivers.push({
+          i: riverId,
+          source,
+          mouth,
+          discharge,
+          length,
+          width,
+          widthFactor,
+          sourceWidth: 0,
+          parent,
+          cells: riverCells
+        });
       }
     }
 
@@ -479,6 +492,10 @@ window.Rivers = (function () {
     return getBasin(parent);
   };
 
+  const getNextId = function (rivers) {
+    return rivers.length ? Math.max(...rivers.map(r => r.i)) + 1 : 1;
+  };
+
   return {
     generate,
     alterHeights,
@@ -493,6 +510,7 @@ window.Rivers = (function () {
     getOffset,
     getApproximateLength,
     getRiverPoints,
-    remove
+    remove,
+    getNextId
   };
 })();
diff --git a/modules/ui/rivers-creator.js b/modules/ui/rivers-creator.js
index 83a4d1b9..a8600917 100644
--- a/modules/ui/rivers-creator.js
+++ b/modules/ui/rivers-creator.js
@@ -74,12 +74,13 @@ function createRiver() {
 
   function addRiver() {
     const {rivers, cells} = pack;
-    const {addMeandering, getApproximateLength, getWidth, getOffset, getName, getRiverPath, getBasin} = Rivers;
+    const {addMeandering, getApproximateLength, getWidth, getOffset, getName, getRiverPath, getBasin, getNextId} =
+      Rivers;
 
     const riverCells = createRiver.cells;
     if (riverCells.length < 2) return tip("Add at least 2 cells", false, "error");
 
-    const riverId = rivers.length ? last(rivers).i + 1 : 1;
+    const riverId = getNextId(rivers);
     const parent = cells.r[last(riverCells)] || riverId;
 
     riverCells.forEach(cell => {
@@ -100,12 +101,30 @@ function createRiver() {
     const name = getName(mouth);
     const basin = getBasin(parent);
 
-    rivers.push({i: riverId, source, mouth, discharge, length, width, widthFactor, sourceWidth, parent, cells: riverCells, basin, name, type: "River"});
+    rivers.push({
+      i: riverId,
+      source,
+      mouth,
+      discharge,
+      length,
+      width,
+      widthFactor,
+      sourceWidth,
+      parent,
+      cells: riverCells,
+      basin,
+      name,
+      type: "River"
+    });
     const id = "river" + riverId;
 
     // render river
     lineGen.curve(d3.curveCatmullRom.alpha(0.1));
-    viewbox.select("#rivers").append("path").attr("id", id).attr("d", getRiverPath(meanderedPoints, widthFactor, sourceWidth));
+    viewbox
+      .select("#rivers")
+      .append("path")
+      .attr("id", id)
+      .attr("d", getRiverPath(meanderedPoints, widthFactor, sourceWidth));
 
     editRiver(id);
   }
diff --git a/modules/ui/tools.js b/modules/ui/tools.js
index 00913e0b..7fbc1ebf 100644
--- a/modules/ui/tools.js
+++ b/modules/ui/tools.js
@@ -626,10 +626,11 @@ function addRiverOnClick() {
     getType,
     getWidth,
     getOffset,
-    getApproximateLength
+    getApproximateLength,
+    getNextId
   } = Rivers;
   const riverCells = [];
-  let riverId = rivers.length ? last(rivers).i + 1 : 1;
+  let riverId = getNextId(rivers);
   let parent = riverId;
 
   const initialFlux = grid.cells.prec[cells.g[i]];
diff --git a/versioning.js b/versioning.js
index 9e10745c..b9e12c80 100644
--- a/versioning.js
+++ b/versioning.js
@@ -1,7 +1,7 @@
 "use strict";
 
 // version and caching control
-const version = "1.89.12"; // generator version, update each time
+const version = "1.89.13"; // generator version, update each time
 
 {
   document.title += " v" + version;