diff --git a/layout/style/Declaration.cpp b/layout/style/Declaration.cpp
index 8638b91071..90baa897b0 100644
--- a/layout/style/Declaration.cpp
+++ b/layout/style/Declaration.cpp
@@ -1086,6 +1086,16 @@ Declaration::GetPropertyValueInternal(
       if (*xValue == *yValue) {
         xValue->AppendToString(eCSSProperty_overflow_x, aValue, aSerialization);
       } else {
+        // Check if either value is clip - if so, shorthand cannot be serialized
+        if (xValue->GetUnit() == eCSSUnit_Enumerated && yValue->GetUnit() == eCSSUnit_Enumerated) {
+          int32_t xVal = xValue->GetIntValue();
+          int32_t yVal = yValue->GetIntValue();
+          if (xVal == NS_STYLE_OVERFLOW_CLIP || yVal == NS_STYLE_OVERFLOW_CLIP) {
+            // When clip is mixed with other values, shorthand cannot be serialized
+            aValue.Truncate();
+            break;
+          }
+        }
         xValue->AppendToString(eCSSProperty_overflow_x, aValue, aSerialization);
         aValue.Append(char16_t(' '));
         yValue->AppendToString(eCSSProperty_overflow_y, aValue, aSerialization);
diff --git a/layout/style/nsRuleNode.cpp b/layout/style/nsRuleNode.cpp
index a593c54b15..5bba2e408a 100644
--- a/layout/style/nsRuleNode.cpp
+++ b/layout/style/nsRuleNode.cpp
@@ -6407,35 +6407,16 @@ nsRuleNode::ComputeDisplayData(void* aStartStruct,
            NS_STYLE_OVERFLOW_VISIBLE);
 
   // CSS3 overflow-x and overflow-y require some fixup as well in some
-  // cases.  NS_STYLE_OVERFLOW_VISIBLE and NS_STYLE_OVERFLOW_CLIP are
-  // meaningful only when used in both dimensions.
+  // cases.  NS_STYLE_OVERFLOW_VISIBLE is meaningful only when used in both dimensions.
+  // NS_STYLE_OVERFLOW_CLIP is now a standard value and should be preserved.
   if (display->mOverflowX != display->mOverflowY &&
       (display->mOverflowX == NS_STYLE_OVERFLOW_VISIBLE ||
-       display->mOverflowX == NS_STYLE_OVERFLOW_CLIP ||
-       display->mOverflowY == NS_STYLE_OVERFLOW_VISIBLE ||
-       display->mOverflowY == NS_STYLE_OVERFLOW_CLIP)) {
+       display->mOverflowY == NS_STYLE_OVERFLOW_VISIBLE)) {
     // We can't store in the rule tree since a more specific rule might
     // change these conditions.
     conditions.SetUncacheable();
 
-    // NS_STYLE_OVERFLOW_CLIP is a deprecated value, so if it's specified
-    // in only one dimension, convert it to NS_STYLE_OVERFLOW_HIDDEN.
-    if (display->mOverflowX == NS_STYLE_OVERFLOW_CLIP) {
-      display->mOverflowX = NS_STYLE_OVERFLOW_HIDDEN;
-    }
-    if (display->mOverflowY == NS_STYLE_OVERFLOW_CLIP) {
-      display->mOverflowY = NS_STYLE_OVERFLOW_HIDDEN;
-    }
-
-    // If 'visible' is specified but doesn't match the other dimension, it
-    // turns into 'auto'.
-    if (display->mOverflowX == NS_STYLE_OVERFLOW_VISIBLE) {
-      display->mOverflowX = NS_STYLE_OVERFLOW_AUTO;
-    }
-    if (display->mOverflowY == NS_STYLE_OVERFLOW_VISIBLE) {
-      display->mOverflowY = NS_STYLE_OVERFLOW_AUTO;
-    }
-    
+    // Note: clip values are now preserved as-is when axes differ
   }
 
   // When 'contain: paint', update overflow from 'visible' to 'clip'.