diff --git a/compat/tdelete.c b/compat/tdelete.c
index aacc63cf498422b2e667eaa5ecc2bdb09d22cc2e..b1f6dbc3bf96da9c7a6de4682120baf0937776bd 100644
--- a/compat/tdelete.c
+++ b/compat/tdelete.c
@@ -17,7 +17,6 @@
 # include <config.h>
 #endif
 
-#include <sys/cdefs.h>
 #include <assert.h>
 #include <stdlib.h>
 
@@ -26,7 +25,7 @@ void *
 tdelete(vkey, vrootp, compar)
 	const void *vkey;	/* key to be deleted */
 	void      **vrootp;	/* address of the root of tree */
-	int       (*compar) __P((const void *, const void *));
+	int       (*compar) (const void *, const void *);
 {
 	node_t **rootp = (node_t **)vrootp;
 	node_t *p, *q, *r;
diff --git a/compat/tdestroy.c b/compat/tdestroy.c
index ecd31718214653e123ee5661fe31650e5307b96f..f943c573d654c6e40ecf4c9fd77dfbd1cd3b9c81 100644
--- a/compat/tdestroy.c
+++ b/compat/tdestroy.c
@@ -20,7 +20,6 @@
 // Do not implement tdestroy if that's the only missing t* function
 #ifndef HAVE_SEARCH_H
 
-#include <sys/cdefs.h>
 #include <assert.h>
 #include <stdlib.h>
 
diff --git a/compat/tfind.c b/compat/tfind.c
index 596051a3f33bdc76e934824a08827780f1d03844..daf69fa884ea0eba802435a3d65e151a13c7c32b 100644
--- a/compat/tfind.c
+++ b/compat/tfind.c
@@ -17,7 +17,6 @@
 # include <config.h>
 #endif
 
-#include <sys/cdefs.h>
 #include <assert.h>
 #include <stdlib.h>
 
@@ -26,7 +25,7 @@ void *
 tfind(vkey, vrootp, compar)
 	const void *vkey;		/* key to be found */
 	const void **vrootp;		/* address of the tree root */
-	int (*compar) __P((const void *, const void *));
+	int (*compar) (const void *, const void *);
 {
 	node_t * const *rootp = (node_t * const*)vrootp;
 
diff --git a/compat/tsearch.c b/compat/tsearch.c
index 1bb24db06f057dcf35451de25a55eeafc2eca69c..625e9b3c90c7623a45ca70db1e396c639f5754a6 100644
--- a/compat/tsearch.c
+++ b/compat/tsearch.c
@@ -17,7 +17,6 @@
 # include <config.h>
 #endif
 
-#include <sys/cdefs.h>
 #include <assert.h>
 #include <stdlib.h>
 
@@ -26,7 +25,7 @@ void *
 tsearch(vkey, vrootp, compar)
 	const void *vkey;		/* key to be located */
 	void **vrootp;			/* address of tree root */
-	int (*compar) __P((const void *, const void *));
+	int (*compar) (const void *, const void *);
 {
 	node_t *q;
 	node_t **rootp = (node_t **)vrootp;
diff --git a/compat/twalk.c b/compat/twalk.c
index b18c2079eec36352559149d2f6068eb3119c8c44..9ee946b1d00f75ad81bbd936b921eac1129d4c9c 100644
--- a/compat/twalk.c
+++ b/compat/twalk.c
@@ -17,18 +17,17 @@
 # include <config.h>
 #endif
 
-#include <sys/cdefs.h>
 #include <assert.h>
 #include <stdlib.h>
 
-static void trecurse __P((const node_t *,
-    void  (*action)(const void *, VISIT, int), int level));
+static void trecurse (const node_t *,
+    void  (*action)(const void *, VISIT, int), int level);
 
 /* Walk the nodes of a tree */
 static void
 trecurse(root, action, level)
 	const node_t *root;	/* Root of the tree to be walked */
-	void (*action) __P((const void *, VISIT, int));
+	void (*action) (const void *, VISIT, int);
 	int level;
 {
 	assert(root != NULL);
@@ -51,7 +50,7 @@ trecurse(root, action, level)
 void
 twalk(vroot, action)
 	const void *vroot;	/* Root of the tree to be walked */
-	void (*action) __P((const void *, VISIT, int));
+	void (*action) (const void *, VISIT, int);
 {
 	if (vroot != NULL && action != NULL)
 		trecurse(vroot, action, 0);