diff --git a/cmake/SignMacApplications.cmake b/cmake/SignMacApplications.cmake
index 816811004..b91e53725 100644
--- a/cmake/SignMacApplications.cmake
+++ b/cmake/SignMacApplications.cmake
@@ -1,6 +1,6 @@
 # This script re-signs all apps after CPack packages them. This is necessary because CPack modifies
 # the library references used by Cockatrice to App relative paths, invalidating the code signature.
-string(LENGTH $ENV{MACOS_CERTIFICATE_NAME} MACOS_CERTIFICATE_NAME_LEN)
+string(LENGTH "$ENV{MACOS_CERTIFICATE_NAME}" MACOS_CERTIFICATE_NAME_LEN)
 
 if(APPLE AND MACOS_CERTIFICATE_NAME_LEN GREATER 0)
   set(APPLICATIONS "cockatrice" "servatrice" "oracle" "dbconverter")