diff --git a/Makefile.am b/Makefile.am
index a0aa115d5..a3e1b34f7 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -52,7 +52,6 @@ src_mpd_LDADD = \
 
 mpd_headers = \
 	src/check.h \
-	src/ack.h \
 	src/command.h \
 	src/conf.h \
 	src/gerror.h \
@@ -94,6 +93,7 @@ src_mpd_SOURCES = \
 	src/CheckAudioFormat.cxx src/CheckAudioFormat.hxx \
 	src/AudioFormat.cxx src/AudioFormat.hxx \
 	src/AudioParser.cxx src/AudioParser.hxx \
+	src/protocol/Ack.hxx \
 	src/protocol/ArgParser.cxx src/protocol/ArgParser.hxx \
 	src/protocol/Result.cxx src/protocol/Result.hxx \
 	src/CommandError.cxx src/CommandError.hxx \
diff --git a/src/ClientFile.cxx b/src/ClientFile.cxx
index 07fa767b0..69bc465b4 100644
--- a/src/ClientFile.cxx
+++ b/src/ClientFile.cxx
@@ -20,7 +20,7 @@
 #include "config.h"
 #include "ClientFile.hxx"
 #include "Client.hxx"
-#include "ack.h"
+#include "protocol/Ack.hxx"
 #include "io_error.h"
 #include "fs/Path.hxx"
 #include "fs/FileSystem.hxx"
diff --git a/src/ack.h b/src/protocol/Ack.hxx
similarity index 100%
rename from src/ack.h
rename to src/protocol/Ack.hxx
diff --git a/src/protocol/Result.hxx b/src/protocol/Result.hxx
index 99d9a2fa0..6766da3d5 100644
--- a/src/protocol/Result.hxx
+++ b/src/protocol/Result.hxx
@@ -22,7 +22,7 @@
 
 #include "check.h"
 #include "gcc.h"
-#include "ack.h"
+#include "Ack.hxx"
 
 class Client;