diff --git a/src/gtk/utilsres.cpp b/src/gtk/utilsres.cpp
index c12f461e11..7c9521fdc9 100644
--- a/src/gtk/utilsres.cpp
+++ b/src/gtk/utilsres.cpp
@@ -40,9 +40,11 @@
 // Yuck this is really BOTH site and platform dependent
 // so we should use some other strategy!
 #ifdef __SUN__
-    #define DEFAULT_XRESOURCE_DIR wxT("/usr/openwin/lib/app-defaults")
+#   define DEFAULT_XRESOURCE_DIR wxT("/usr/openwin/lib/app-defaults")
+// prototype missing in header files on Solaris 2.5
+extern int gethostname(char *name, size_t len);
 #else
-    #define DEFAULT_XRESOURCE_DIR wxT("/usr/lib/X11/app-defaults")
+#   define DEFAULT_XRESOURCE_DIR wxT("/usr/lib/X11/app-defaults")
 #endif
 
 //-----------------------------------------------------------------------------
diff --git a/src/gtk1/utilsres.cpp b/src/gtk1/utilsres.cpp
index c12f461e11..7c9521fdc9 100644
--- a/src/gtk1/utilsres.cpp
+++ b/src/gtk1/utilsres.cpp
@@ -40,9 +40,11 @@
 // Yuck this is really BOTH site and platform dependent
 // so we should use some other strategy!
 #ifdef __SUN__
-    #define DEFAULT_XRESOURCE_DIR wxT("/usr/openwin/lib/app-defaults")
+#   define DEFAULT_XRESOURCE_DIR wxT("/usr/openwin/lib/app-defaults")
+// prototype missing in header files on Solaris 2.5
+extern int gethostname(char *name, size_t len);
 #else
-    #define DEFAULT_XRESOURCE_DIR wxT("/usr/lib/X11/app-defaults")
+#   define DEFAULT_XRESOURCE_DIR wxT("/usr/lib/X11/app-defaults")
 #endif
 
 //-----------------------------------------------------------------------------