diff --git a/src/os_amiga.h b/src/os_amiga.h
index 0395bce..69a1523 100644
--- a/src/os_amiga.h
+++ b/src/os_amiga.h
@@ -56,6 +56,9 @@
 # define TEMPNAMELEN	12
 #endif
 
+/* cproto fails on missing include files */
+#ifndef PROTO
+
 #include <exec/types.h>
 #include <libraries/dos.h>
 #include <libraries/dosextens.h>
@@ -67,6 +70,8 @@
 # include <proto/intuition.h>
 #endif
 
+#endif /* PROTO */
+
 #define FNAME_ILLEGAL ";*?`#%" /* illegal characters in a file name */
 
 /*
@@ -85,6 +90,7 @@
 # include <unistd.h>
 #endif
 
+#ifndef PROTO
 /*
  * arpbase.h must be included before functions.h
  */
@@ -92,6 +98,8 @@
 # include <libraries/arpbase.h>
 #endif
 
+#endif /* PROTO */
+
 /*
  * This won't be needed if you have a version of Lattice 4.01 without broken
  * break signal handling.