diff --git a/src/unix/utilsunx.cpp b/src/unix/utilsunx.cpp
index 6115ef3330..35a7529461 100644
--- a/src/unix/utilsunx.cpp
+++ b/src/unix/utilsunx.cpp
@@ -126,9 +126,9 @@
 // headers - please add your system here if it is the case for your OS.
 // SunOS < 5.6 (i.e. Solaris < 2.6) and DG-UX are like this.
 #if !defined(HAVE_USLEEP) && \
-    (defined(__SUN__) && !defined(__SunOs_5_6) && \
+    ((defined(__SUN__) && !defined(__SunOs_5_6) && \
                          !defined(__SunOs_5_7) && !defined(__SUNPRO_CC)) || \
-     defined(__osf__) || defined(__EMX__)
+     defined(__osf__) || defined(__EMX__))
     extern "C"
     {
         #ifdef __SUN__