diff --git a/app/ui.js b/app/ui.js
index ef5a2245a..c5eff3c13 100644
--- a/app/ui.js
+++ b/app/ui.js
@@ -1104,6 +1104,7 @@ const UI = {
         if (val === null) {
             val = WebUtil.readSetting(name, defVal);
         }
+        val = UI.sanitizeSetting(name, val);
         WebUtil.setSetting(name, val);
         UI.updateSetting(name);
         return val;
@@ -1111,6 +1112,7 @@ const UI = {
 
     // Set the new value, update and disable form control setting
     forceSetting(name, val, disable=true) {
+        val = UI.sanitizeSetting(name, val);
         WebUtil.setSetting(name, val);
         UI.updateSetting(name);
         if (disable) {
@@ -1149,6 +1151,26 @@ const UI = {
         }
     },
 
+    // Ensure settings stay within supported bounds
+    sanitizeSetting(name, value) {
+        switch (name) {
+            case 'framerate': {
+                let numeric = parseInt(value, 10);
+                if (!Number.isFinite(numeric)) {
+                    numeric = 30;
+                }
+                if (numeric < 10) {
+                    numeric = 10;
+                } else if (numeric > 120) {
+                    numeric = 120;
+                }
+                return String(numeric);
+            }
+            default:
+                return value;
+        }
+    },
+
     // Save control setting to cookie
     saveSetting(name) {
         const ctrl = document.getElementById('noVNC_setting_' + name);
@@ -1160,6 +1182,13 @@ const UI = {
         } else {
             val = ctrl.value;
         }
+        const sanitized = UI.sanitizeSetting(name, val);
+        if (sanitized !== val) {
+            if (ctrl && typeof ctrl.value !== 'undefined') {
+                ctrl.value = sanitized;
+            }
+            val = sanitized;
+        }
         WebUtil.writeSetting(name, val);
         //Log.Debug("Setting saved '" + name + "=" + val + "'");
         return val;
@@ -1179,8 +1208,12 @@ const UI = {
                 val = true;
             }
         }
-
-        return val;
+        const sanitized = UI.sanitizeSetting(name, val);
+        const currentStr = (val === null || typeof val === 'undefined') ? null : String(val);
+        if (sanitized !== val && sanitized !== currentStr) {
+            WebUtil.writeSetting(name, sanitized);
+        }
+        return sanitized;
     },
 
     // These helpers compensate for the lack of parent-selectors and
diff --git a/core/encodings.js b/core/encodings.js
index af2f4493d..e59f60c1f 100644
--- a/core/encodings.js
+++ b/core/encodings.js
@@ -46,8 +46,8 @@ export const encodings = {
     pseudoEncodingVideoTimeLevel0: -870,
     pseudoEncodingVideoTimeLevel100: -770,
 
-    pseudoEncodingFrameRateLevel10: -2048,
-    pseudoEncodingFrameRateLevel60: -1998,
+    pseudoEncodingFrameRateLevel10: -4096,
+    pseudoEncodingFrameRateLevel120: -3986,
     pseudoEncodingMaxVideoResolution: -1997,
     pseudoEncodingVideoScalingLevel0: -1996,
     pseudoEncodingVideoScalingLevel9: -1987,
diff --git a/core/rfb.js b/core/rfb.js
index 73e6bc809..9a213948c 100644
--- a/core/rfb.js
+++ b/core/rfb.js
@@ -622,8 +622,8 @@ export default class RFB extends EventTargetMixin {
 
     get frameRate() { return this._frameRate; }
     set frameRate(value) {
-        if (!Number.isInteger(value) || value < 1 || value > 120) {
-            Log.Error("frame rate must be an integer between 1 and 120");
+        if (!Number.isInteger(value) || value < 10 || value > 120) {
+            Log.Error("frame rate must be an integer between 10 and 120");
             return;
         }
 
@@ -3179,7 +3179,11 @@ export default class RFB extends EventTargetMixin {
         encs.push(encodings.pseudoEncodingVideoTimeLevel0 + this.videoTime);
         encs.push(encodings.pseudoEncodingVideoOutTimeLevel1 + this.videoOutTime - 1);
         encs.push(encodings.pseudoEncodingVideoScalingLevel0 + this.videoScaling);
-        encs.push(encodings.pseudoEncodingFrameRateLevel10 + this.frameRate - 10);
+        const frameRate = Math.round(Math.max(10, Math.min(120, this.frameRate)));
+        if (frameRate !== this.frameRate) {
+            Log.Warn("Frame rate value " + this.frameRate + " adjusted to " + frameRate);
+        }
+        encs.push(encodings.pseudoEncodingFrameRateLevel10 + frameRate - 10);
         encs.push(encodings.pseudoEncodingMaxVideoResolution);
         
 	// preferBandwidth choses preset settings. Since we expose all the settings, lets not pass this
diff --git a/index.html b/index.html
index 24956467a..79f3b3ca0 100644
--- a/index.html
+++ b/index.html
@@ -387,7 +387,7 @@ <h1 class="noVNC_logo">
                                             </li>
                                             <li>
                                                 <label for="noVNC_setting_framerate">Frame Rate:</label>
-                                                <input id="noVNC_setting_framerate" type="number" min="1" max="120" value="30">
+                                                <input id="noVNC_setting_framerate" type="number" min="10" max="120" step="1" value="30">
                                             </li>
                                             <li>
                                                 <label for="noVNC_setting_jpeg_video_quality">Video JPEG Quality:</label>