diff --git a/test/ASTMerge/Inputs/interface1.m b/test/ASTMerge/Inputs/interface1.m
index a508bc1..029dad3 100644
--- a/test/ASTMerge/Inputs/interface1.m
+++ b/test/ASTMerge/Inputs/interface1.m
@@ -68,3 +68,8 @@
 @protocol P2 <P0>
 - (float)wibble:(int)a1 second:(int)a2;
 @end
+
+// Forward-declared interfaces
+@class I10, I11;
+@interface I12
+@end
diff --git a/test/ASTMerge/Inputs/interface2.m b/test/ASTMerge/Inputs/interface2.m
index d79f77d..30de981 100644
--- a/test/ASTMerge/Inputs/interface2.m
+++ b/test/ASTMerge/Inputs/interface2.m
@@ -67,3 +67,8 @@
 @protocol P2 <P0>
 - (float)wibble:(int)a1 second:(int)a2;
 @end
+
+// Forward-declared interface
+@class I12, I10;
+@interface I11
+@end