diff --git a/build_files/build_environment/cmake/versions.cmake b/build_files/build_environment/cmake/versions.cmake
index 64e87f2830c..aedaea456fd 100644
--- a/build_files/build_environment/cmake/versions.cmake
+++ b/build_files/build_environment/cmake/versions.cmake
@@ -48,11 +48,11 @@ set(PTHREADS_SHA512 9c06e85310766834370c3dceb83faafd397da18a32411ca7645c8eb6b949
 set(ILMBASE_VERSION 2.3.0)
 if (WIN32)
 	if(BUILD_MODE STREQUAL Release)
-		set(ILMBASE_VERSION_POSTFIX -2_3_s)
-		set(OPENEXR_VERSION_POSTFIX -2_3_s)
+		set(ILMBASE_VERSION_POSTFIX _s)
+		set(OPENEXR_VERSION_POSTFIX _s)
 	else()
-		set(ILMBASE_VERSION_POSTFIX -2_3_s_d)
-		set(OPENEXR_VERSION_POSTFIX -2_3_s_d)
+		set(ILMBASE_VERSION_POSTFIX _s_d)
+		set(OPENEXR_VERSION_POSTFIX _s_d)
 	endif()
 else()
 	set(ILMBASE_VERSION_POSTFIX)
@@ -271,5 +271,7 @@ set(PUGIXML_VERSION 1.9)
 set(PUGIXML_URI https://github.com/zeux/pugixml/archive/v1.9.tar.gz)
 set(PUGIXML_HASH 9346ca1dce2c48f1748c12fdac41a714)
 
-
+set(FLEXBISON_VERSION 2.5.5)
+set(FLEXBISON_URI http://prdownloads.sourceforge.net/winflexbison//win_flex_bison-2.5.5.zip)
+set(FLEXBISON_HASH d87a3938194520d904013abef3df10ce)