--- a/src/pthreads.c
+++ b/src/pthreads.c
@@ -79,6 +79,6 @@
 #define alloca _alloca
 #elif !defined(alloca) && defined(__GNUC__)
 #define alloca(s) __builtin_alloca(s)
-#else
+#elif !defined(alloca)
 #include <alloca.h>
 #endif