diff --git a/gdb/xm-sun3os4.h b/gdb/xm-sun3os4.h
index d7d1c958d04..ac61c6cb230 100644
--- a/gdb/xm-sun3os4.h
+++ b/gdb/xm-sun3os4.h
@@ -26,3 +26,5 @@ Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  */
    the area occupied by the shared libraries.  Sun knows about this bug
    but has no obvious fix for it.  */
 #define BROKEN_LARGE_ALLOCA
+
+#define HAVE_STRSTR
diff --git a/gdb/xm-sun4os4.h b/gdb/xm-sun4os4.h
index 75f10375079..b2f3de6e4ea 100644
--- a/gdb/xm-sun4os4.h
+++ b/gdb/xm-sun4os4.h
@@ -26,3 +26,5 @@ Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  */
    the area occupied by the shared libraries.  Sun knows about this bug
    but has no obvious fix for it.  */
 #define BROKEN_LARGE_ALLOCA
+
+#define HAVE_STRSTR