diff --git a/CMakeLists.txt b/CMakeLists.txt
index 09725af..09ae69d 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -128,7 +128,7 @@ endif()
 
 # parse the full version number from zlib.h and include in ZLIB_FULL_VERSION
 file(READ ${CMAKE_CURRENT_SOURCE_DIR}/zlib.h _zlib_h_contents)
-string(REGEX REPLACE ".*#define[ \t]+ZLIB_VERSION[ \t]+\"([0-9A-Za-z.]+)\".*"
+string(REGEX REPLACE ".*#define[ \t]+ZLIB_VERSION[ \t]+\"([-0-9A-Za-z.]+)\".*"
     "\\1" ZLIB_FULL_VERSION ${_zlib_h_contents})
 
 if(MINGW)