diff --git a/lib/canon-host.c b/lib/canon-host.c
index 9d968a035..180057c3f 100644
--- a/lib/canon-host.c
+++ b/lib/canon-host.c
@@ -43,7 +43,9 @@
 # include <arpa/inet.h>
 #endif
 
+#ifndef strdup
 char *strdup ();
+#endif
 void free ();
 
 /* Returns the canonical hostname associated with HOST (allocated in a static
diff --git a/lib/path-concat.c b/lib/path-concat.c
index ac2c8b8d5..8c4bbb4e8 100644
--- a/lib/path-concat.c
+++ b/lib/path-concat.c
@@ -32,7 +32,9 @@
 #include <sys/types.h>
 
 char *malloc ();
+#ifndef strdup
 char *strdup ();
+#endif
 
 #ifndef DIRECTORY_SEPARATOR
 # define DIRECTORY_SEPARATOR '/'