diff --git a/mozilla/layout/generic/nsHTMLReflowState.cpp b/mozilla/layout/generic/nsHTMLReflowState.cpp
index 711b1f356da..4b74544e8ee 100644
--- a/mozilla/layout/generic/nsHTMLReflowState.cpp
+++ b/mozilla/layout/generic/nsHTMLReflowState.cpp
@@ -107,6 +107,8 @@ nsHTMLReflowState::operator=(const nsHTMLReflowState &aOther)
   // to |this|.
   if (aOther.mCBReflowState == &aOther)
     mCBReflowState = this;
+
+  return *this;
 }
 
 // Initialize a <b>root</b> reflow state with a rendering context to
diff --git a/mozilla/layout/html/base/src/nsHTMLReflowState.cpp b/mozilla/layout/html/base/src/nsHTMLReflowState.cpp
index 711b1f356da..4b74544e8ee 100644
--- a/mozilla/layout/html/base/src/nsHTMLReflowState.cpp
+++ b/mozilla/layout/html/base/src/nsHTMLReflowState.cpp
@@ -107,6 +107,8 @@ nsHTMLReflowState::operator=(const nsHTMLReflowState &aOther)
   // to |this|.
   if (aOther.mCBReflowState == &aOther)
     mCBReflowState = this;
+
+  return *this;
 }
 
 // Initialize a <b>root</b> reflow state with a rendering context to