diff --git a/dom/html/TextControlState.cpp b/dom/html/TextControlState.cpp
index 87cba87d1de9..e178595b4500 100644
--- a/dom/html/TextControlState.cpp
+++ b/dom/html/TextControlState.cpp
@@ -2069,6 +2069,17 @@ void TextControlState::SetSelectionRange(
   bool changed = false;
   nsresult rv = NS_OK;  // For the ScrollSelectionIntoView() return value.
   if (IsSelectionCached()) {
+    nsAutoString value;
+    // XXXbz is "false" the right thing to pass here?  Hard to tell, given the
+    // various mismatches between our impl and the spec.
+    GetValue(value, false);
+    uint32_t length = value.Length();
+    if (aStart > length) {
+      aStart = length;
+    }
+    if (aEnd > length) {
+      aEnd = length;
+    }
     SelectionProperties& props = GetSelectionProperties();
     changed = props.GetStart() != aStart || props.GetEnd() != aEnd ||
               props.GetDirection() != aDirection;
@@ -2882,7 +2893,6 @@ bool TextControlState::SetValueWithoutTextEditor(
             aHandlingSetValue.GetSetValueFlags()));
 
         SelectionProperties& props = GetSelectionProperties();
-        props.SetMaxLength(aHandlingSetValue.GetSettingValue().Length());
         if (aHandlingSetValue.GetSetValueFlags() &
             eSetValue_MoveCursorToEndIfValueChanged) {
           props.SetStart(aHandlingSetValue.GetSettingValue().Length());
@@ -2893,6 +2903,13 @@ bool TextControlState::SetValueWithoutTextEditor(
           props.SetStart(0);
           props.SetEnd(0);
           props.SetDirection(nsITextControlFrame::eForward);
+        } else {
+          // Make sure our cached selection position is not outside the new
+          // value.
+          props.SetStart(std::min(
+              props.GetStart(), aHandlingSetValue.GetSettingValue().Length()));
+          props.SetEnd(std::min(props.GetEnd(),
+                                aHandlingSetValue.GetSettingValue().Length()));
         }
       }
 
diff --git a/dom/html/TextControlState.h b/dom/html/TextControlState.h
index 39dbf1a45c45..744ad3eb3707 100644
--- a/dom/html/TextControlState.h
+++ b/dom/html/TextControlState.h
@@ -284,12 +284,12 @@ class TextControlState final : public SupportsWeakPtr {
     uint32_t GetStart() const { return mStart; }
     void SetStart(uint32_t value) {
       mIsDirty = true;
-      mStart = std::min(value, mMaxLength);
+      mStart = value;
     }
     uint32_t GetEnd() const { return mEnd; }
     void SetEnd(uint32_t value) {
       mIsDirty = true;
-      mEnd = std::min(value, mMaxLength);
+      mEnd = value;
     }
     nsITextControlFrame::SelectionDirection GetDirection() const {
       return mDirection;
@@ -298,20 +298,13 @@ class TextControlState final : public SupportsWeakPtr {
       mIsDirty = true;
       mDirection = value;
     }
-    void SetMaxLength(uint32_t aMax) {
-      mMaxLength = aMax;
-      // recompute against the new max length
-      SetStart(GetStart());
-      SetEnd(GetEnd());
-    }
-
     // return true only if mStart, mEnd, or mDirection have been modified,
     // or if SetIsDirty() was explicitly called.
     bool IsDirty() const { return mIsDirty; }
     void SetIsDirty() { mIsDirty = true; }
 
    private:
-    uint32_t mStart, mEnd, mMaxLength;
+    uint32_t mStart, mEnd;
     bool mIsDirty = false;
     nsITextControlFrame::SelectionDirection mDirection;
   };
diff --git a/testing/web-platform/tests/html/semantics/forms/textfieldselection/selection-start-end.html b/testing/web-platform/tests/html/semantics/forms/textfieldselection/selection-start-end.html
index 919d1a4d6583..4bcecf234cc0 100644
--- a/testing/web-platform/tests/html/semantics/forms/textfieldselection/selection-start-end.html
+++ b/testing/web-platform/tests/html/semantics/forms/textfieldselection/selection-start-end.html
@@ -144,31 +144,6 @@
     }
   }, "selectionEnd edge-case values");
 
-  test(() => {
-    for (const el of createTestElements(testValue)) {
-      el.selectionStart = 200;
-      assert_equals(el.selectionStart, testValue.length);
-      el.remove();
-    }
-  }, "selectionStart should be clamped by the current value length");
-
-  test(() => {
-    for (const el of createTestElements(testValue)) {
-      el.selectionStart = 300;
-      assert_equals(el.selectionEnd, testValue.length);
-      el.remove();
-    }
-  }, "selectionEnd should be clamped by the current value length");
-
-  test(() => {
-    for (const el of createTestElements(testValue)) {
-      el.setSelectionRange(200, 300);
-      assert_equals(el.selectionStart, testValue.length);
-      assert_equals(el.selectionEnd, testValue.length);
-      el.remove();
-    }
-  }, "setSelectionRange should be clamped by the current value length");
-
   test(() => {
     for (let el of createTestElements(testValue)) {
       const start = 1;