diff --git a/src/proto.h b/src/proto.h
index e9e5efcbc5..3c34fe8132 100644
--- a/src/proto.h
+++ b/src/proto.h
@@ -73,7 +73,9 @@ extern int _stricoll(char *a, char *b);
 # include "if_cscope.pro"
 # include "debugger.pro"
 # include "dict.pro"
+# ifdef FEAT_DIFF
 # include "diff.pro"
+# endif
 # include "linematch.pro"
 # include "digraph.pro"
 # include "drawline.pro"
diff --git a/src/proto/diff.pro b/src/proto/diff.pro
index e87e81b8c4..3a4929b0cc 100644
--- a/src/proto/diff.pro
+++ b/src/proto/diff.pro
@@ -22,10 +22,8 @@ int diffopt_horizontal(void);
 int diffopt_hiddenoff(void);
 int diffopt_closeoff(void);
 void diff_update_line(linenr_T lnum);
-#ifdef FEAT_DIFF
 int diff_change_parse(diffline_T *diffline, diffline_change_T *change, int *change_start, int *change_end);
 int diff_find_change(win_T *wp, linenr_T lnum, diffline_T *diffline);
-#endif
 int diff_infold(win_T *wp, linenr_T lnum);
 void nv_diffgetput(int put, long count);
 void ex_diffgetput(exarg_T *eap);
diff --git a/src/structs.h b/src/structs.h
index 7748d57561..d7b4580774 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -3606,7 +3606,7 @@ struct file_buffer
 }; // file_buffer
 
 
-#ifdef FEAT_DIFF
+#if defined(FEAT_DIFF) || defined(PROTO)
 /*
  * Stuff for diff mode.
  */
diff --git a/src/version.c b/src/version.c
index 3c38765d43..7e4682cc8c 100644
--- a/src/version.c
+++ b/src/version.c
@@ -719,6 +719,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1637,
 /**/
     1636,
 /**/