diff --git a/test/ASTMerge/Inputs/interface1.m b/test/ASTMerge/Inputs/interface1.m
index 029dad3..7e9935d 100644
--- a/test/ASTMerge/Inputs/interface1.m
+++ b/test/ASTMerge/Inputs/interface1.m
@@ -73,3 +73,9 @@
 @class I10, I11;
 @interface I12
 @end
+
+// Forward-declared protocols
+@protocol P3, P5;
+@protocol P4
+- (double)honk:(int)a;
+@end
diff --git a/test/ASTMerge/Inputs/interface2.m b/test/ASTMerge/Inputs/interface2.m
index 30de981..bef7fb8 100644
--- a/test/ASTMerge/Inputs/interface2.m
+++ b/test/ASTMerge/Inputs/interface2.m
@@ -72,3 +72,9 @@
 @class I12, I10;
 @interface I11
 @end
+
+// Forward-declared protocols
+@protocol P3, P4;
+@protocol P5
+- (double)honk:(int)a;
+@end