diff --git a/mozilla/content/html/style/src/nsCSSRules.cpp b/mozilla/content/html/style/src/nsCSSRules.cpp
index 6e03090eb70..0751e2ceb55 100644
--- a/mozilla/content/html/style/src/nsCSSRules.cpp
+++ b/mozilla/content/html/style/src/nsCSSRules.cpp
@@ -695,7 +695,7 @@ nsCSSGroupRule::SetStyleSheet(nsICSSStyleSheet* aSheet)
 }
 
 #ifdef DEBUG
-nsresult
+NS_IMETHODIMP
 nsCSSGroupRule::List(FILE* out, PRInt32 aIndent) const
 {
   fputs(" {\n", out);
diff --git a/mozilla/layout/style/nsCSSRules.cpp b/mozilla/layout/style/nsCSSRules.cpp
index 6e03090eb70..0751e2ceb55 100644
--- a/mozilla/layout/style/nsCSSRules.cpp
+++ b/mozilla/layout/style/nsCSSRules.cpp
@@ -695,7 +695,7 @@ nsCSSGroupRule::SetStyleSheet(nsICSSStyleSheet* aSheet)
 }
 
 #ifdef DEBUG
-nsresult
+NS_IMETHODIMP
 nsCSSGroupRule::List(FILE* out, PRInt32 aIndent) const
 {
   fputs(" {\n", out);