diff --git a/physfs_internal.h b/physfs_internal.h
index 334ee6b..7784d7f 100644
--- a/physfs_internal.h
+++ b/physfs_internal.h
@@ -29,6 +29,10 @@
 #include <malloc.h>
 #endif
 
+#if defined(__sun) || defined(sun)
+#include <alloca.h>
+#endif
+
 #ifdef __cplusplus
 extern "C" {
 #endif