diff --git a/configure.ac b/configure.ac
index 8fc4a9aa6..6e021f9ef 100644
--- a/configure.ac
+++ b/configure.ac
@@ -193,7 +193,7 @@ network_LIBS="$LIBS"
 LIBS=""
 
 dnl check for some default libraries
-AC_SEARCH_LIBS(cos, m)
+AC_SEARCH_LIBS(cos, [fastm m])
 AC_SEARCH_LIBS(dlclose, dl)
 
 base_LIBS="$LIBS"
diff --git a/src/AIModel/AIAircraft.cxx b/src/AIModel/AIAircraft.cxx
index 08623551b..bbc5b9bfa 100644
--- a/src/AIModel/AIAircraft.cxx
+++ b/src/AIModel/AIAircraft.cxx
@@ -36,7 +36,7 @@
 #ifdef _MSC_VER
 #  include <float.h>
 #  define finite _finite
-#elif defined(sun) || defined(sgi)
+#elif defined(__sun) || defined(sgi)
 #  include <ieeefp.h>
 #endif
 
diff --git a/src/Cockpit/hud.cxx b/src/Cockpit/hud.cxx
index 043eeb8ee..98b4f1394 100644
--- a/src/Cockpit/hud.cxx
+++ b/src/Cockpit/hud.cxx
@@ -58,7 +58,7 @@
 #include <Main/fg_props.hxx>
 #include <Scenery/scenery.hxx>
 
-#if defined ( __sun__ ) || defined ( __sgi )
+#if defined (__sun) || defined ( __sgi )
 extern "C" {
     extern void *memmove(void *, const void *, size_t);
 }
diff --git a/src/Main/metar_main.cxx b/src/Main/metar_main.cxx
index 0f79ec83c..36567ffb3 100644
--- a/src/Main/metar_main.cxx
+++ b/src/Main/metar_main.cxx
@@ -31,7 +31,7 @@
 using namespace std;
 
 // text color
-#if defined(__linux__) || defined( __sun__ ) || defined(__CYGWIN__) \
+#if defined(__linux__) || defined(__sun) || defined(__CYGWIN__) \
     || defined( __FreeBSD__ ) || defined ( sgi )
 #	define R "\033[31;1m"		// red
 #	define G "\033[32;1m"		// green
diff --git a/tests/test-mktime.cxx b/tests/test-mktime.cxx
index 24e328d23..037e94e5e 100644
--- a/tests/test-mktime.cxx
+++ b/tests/test-mktime.cxx
@@ -75,7 +75,7 @@ time_t get_start_gmt(int year) {
 #else // ! defined ( MK_TIME_IS_GMT )
 
     // timezone seems to work as a proper offset for Linux & Solaris
-#  if defined( __linux__ ) || defined( __sun__ ) || defined( __CYGWIN__ )
+#  if defined( __linux__ ) || defined(__sun) || defined( __CYGWIN__ )
 #   define TIMEZONE_OFFSET_WORKS 1
 #  endif