diff --git a/CMakeLists.txt b/CMakeLists.txt
index b1a26ff3e8..88c9bb6bde 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1218,6 +1218,7 @@ CHECK_TYPE_SIZE("ssize_t"   SIZEOF_SSIZE_T)
 if(SIZEOF_SSIZE_T)
   set(HAVE_SSIZE_T TRUE)
 endif(SIZEOF_SSIZE_T)
+
 CHECK_TYPE_SIZE("ptrdiff_t" SIZEOF_PTRDIFF_T)
 if(SIZEOF_PTRDIFF_T)
   set(HAVE_PTRDIFF_T TRUE)
diff --git a/config.h.cmake.in b/config.h.cmake.in
index 00e062f760..cadc16d6fa 100644
--- a/config.h.cmake.in
+++ b/config.h.cmake.in
@@ -582,6 +582,9 @@ with zip */
 /* The size of `size_t', as computed by sizeof. */
 #cmakedefine SIZEOF_SIZE_T ${SIZEOF_SIZE_T}
 
+/* The size of `ssize_t', as computed by sizeof. */
+#cmakedefine SIZEOF_SSIZE_T ${SIZEOF_SSIZE_T}
+
 /* The size of `uint', as computed by sizeof. */
 #cmakedefine SIZEOF_UINT ${SIZEOF_UINT}
 
diff --git a/include/ncconfigure.h b/include/ncconfigure.h
index 2c766c8e00..8c17752d6b 100644
--- a/include/ncconfigure.h
+++ b/include/ncconfigure.h
@@ -28,9 +28,6 @@
 #ifdef HAVE_UNISTD_H
 #include <unistd.h>
 #endif
-#ifdef HAVE_UNISTD_H
-#include <unistd.h>
-#endif
 #ifdef __APPLE__ /* GCC strikes again */
 #ifndef uint
 typedef unsigned int uint;