diff --git a/NEWS b/NEWS
index ca013f1b..a12f8b4f 100644
--- a/NEWS
+++ b/NEWS
@@ -1,3 +1,10 @@
+What's new in psycopg 2.5.1
+---------------------------
+
+- Fixed build on Solaris 10 and 11 where the round() function is already
+  declared (:ticket:`#146`).
+
+
 What's new in psycopg 2.5
 -------------------------
 
diff --git a/psycopg/config.h b/psycopg/config.h
index f3094493..45157709 100644
--- a/psycopg/config.h
+++ b/psycopg/config.h
@@ -141,7 +141,10 @@ static int pthread_mutex_init(pthread_mutex_t *mutex, void* fake)
 #endif
 #endif
 
-#if (defined(__FreeBSD__) && __FreeBSD_version < 503000) || (defined(_WIN32) && !defined(__GNUC__)) || defined(__sun__) || defined(sun)
+#if (defined(__FreeBSD__) && __FreeBSD_version < 503000) \
+    || (defined(_WIN32) && !defined(__GNUC__)) \
+    || (defined(sun) || defined(__sun__)) \
+        && (defined(__SunOS_5_8) || defined(__SunOS_5_9))
 /* what's this, we have no round function either? */
 static double round(double num)
 {