diff --git a/Signal.xcodeproj/project.pbxproj b/Signal.xcodeproj/project.pbxproj
index a292ebe16..2ed9d2c97 100644
--- a/Signal.xcodeproj/project.pbxproj
+++ b/Signal.xcodeproj/project.pbxproj
@@ -4016,7 +4016,10 @@
 				HEADER_SEARCH_PATHS = "";
 				IPHONEOS_DEPLOYMENT_TARGET = 9.0;
 				ONLY_ACTIVE_ARCH = YES;
-				OTHER_CFLAGS = "-fobjc-arc-exceptions";
+				OTHER_CFLAGS = (
+					"-fobjc-arc-exceptions",
+					"-Werror=protocol",
+				);
 				SDKROOT = iphoneos;
 				SWIFT_VERSION = 4.0;
 				VALIDATE_PRODUCT = YES;
@@ -4089,6 +4092,7 @@
 				OTHER_CFLAGS = (
 					"-DNS_BLOCK_ASSERTIONS=1",
 					"-fobjc-arc-exceptions",
+					"-Werror=protocol",
 				);
 				SDKROOT = iphoneos;
 				SWIFT_OPTIMIZATION_LEVEL = "-Owholemodule";