diff --git a/layout/generic/nsBlockReflowContext.h b/layout/generic/nsBlockReflowContext.h
index a6aaaec7536d..30161234b2c0 100644
--- a/layout/generic/nsBlockReflowContext.h
+++ b/layout/generic/nsBlockReflowContext.h
@@ -43,7 +43,7 @@
 
 class nsBlockFrame;
 class nsBlockReflowState;
-class nsHTMLReflowState;
+struct nsHTMLReflowState;
 class nsLineBox;
 class nsIFrame;
 class nsPresContext;
diff --git a/layout/html/base/src/nsBlockReflowContext.h b/layout/html/base/src/nsBlockReflowContext.h
index a6aaaec7536d..30161234b2c0 100644
--- a/layout/html/base/src/nsBlockReflowContext.h
+++ b/layout/html/base/src/nsBlockReflowContext.h
@@ -43,7 +43,7 @@
 
 class nsBlockFrame;
 class nsBlockReflowState;
-class nsHTMLReflowState;
+struct nsHTMLReflowState;
 class nsLineBox;
 class nsIFrame;
 class nsPresContext;