diff --git a/lib/src/gsasl.h b/lib/src/gsasl.h
index 1b5072c2..999555f6 100644
--- a/lib/src/gsasl.h
+++ b/lib/src/gsasl.h
@@ -33,7 +33,9 @@
 
 # include <stdio.h>		/* FILE */
 # include <stddef.h>		/* size_t */
+#ifndef _WIN32
 # include <unistd.h>		/* ssize_t */
+#endif
 
 /* Get version symbols. */
 # include <gsasl-version.h>