diff --git a/CMakeLists.txt b/CMakeLists.txt
index f1070bfc6..a8724632b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -11,7 +11,7 @@ set (GTSAM_PRERELEASE_VERSION "a0")
 math (EXPR GTSAM_VERSION_NUMERIC "10000 * ${GTSAM_VERSION_MAJOR} + 100 * ${GTSAM_VERSION_MINOR} + ${GTSAM_VERSION_PATCH}")
 
 if (DEFINED ENV{DEVELOP})
-    set (GTSAM_VERSION_STRING "${GTSAM_VERSION_MAJOR}.${GTSAM_VERSION_MINOR}${GTSAM_PRERELEASE_VERSION}.$ENV{COMMIT_HASH}")
+    set (GTSAM_VERSION_STRING "${GTSAM_VERSION_MAJOR}.${GTSAM_VERSION_MINOR}${GTSAM_PRERELEASE_VERSION}+$ENV{COMMIT_HASH}")
     set (SETUP_NAME "gtsam-develop")
 elseif ("${GTSAM_PRERELEASE_VERSION}" STREQUAL "")
     set (GTSAM_VERSION_STRING "${GTSAM_VERSION_MAJOR}.${GTSAM_VERSION_MINOR}.${GTSAM_VERSION_PATCH}")