diff --git a/src/libzzuf/lib-mem.c b/src/libzzuf/lib-mem.c
index a82fc6f..3c84a62 100644
--- a/src/libzzuf/lib-mem.c
+++ b/src/libzzuf/lib-mem.c
@@ -36,7 +36,7 @@
 /* Need this to include <libc.h> on OS X */
 #define _DARWIN_C_SOURCE
 /* Use this to get posix_memalign */
-#if defined HAVE_POSIX_MEMALIGN
+#if defined HAVE_POSIX_MEMALIGN && !defined __sun
 #   undef _XOPEN_SOURCE
 #   define _XOPEN_SOURCE 600
 #endif
diff --git a/src/zzcat.c b/src/zzcat.c
index 9317e0e..5bd6cdf 100644
--- a/src/zzcat.c
+++ b/src/zzcat.c
@@ -22,6 +22,8 @@
 #define _INCLUDE_POSIX_SOURCE
 /* Needed for fgets_unlocked() */
 #define _GNU_SOURCE
+/* Needed for getc_unlocked() on OpenSolaris */
+#define __EXTENSIONS__
 
 #if defined HAVE_STDINT_H
 #   include <stdint.h>