diff --git a/cmake/ExternalAntlr4Cpp.cmake b/cmake/ExternalAntlr4Cpp.cmake
index f53e855..4689ae1 100644
--- a/cmake/ExternalAntlr4Cpp.cmake
+++ b/cmake/ExternalAntlr4Cpp.cmake
@@ -8,7 +8,9 @@ include(ExternalProject)
 
 set(ANTLR4_ROOT ${CMAKE_CURRENT_BINARY_DIR}/antlr4_runtime/src/antlr4_runtime)
 set(ANTLR4_INCLUDE_DIRS ${ANTLR4_ROOT}/runtime/Cpp/runtime/src)
-set(ANTLR4_GIT_REPOSITORY https://github.com/antlr/antlr4.git)
+if (NOT DEFINED ANTLR4_GIT_REPOSITORY)
+    set(ANTLR4_GIT_REPOSITORY https://github.com/antlr/antlr4.git)
+endif()
 if(NOT DEFINED ANTLR4_TAG)
     # Set to branch name to keep library updated at the cost of needing to rebuild after 'clean'
     # Set to commit hash to keep the build stable and does not need to rebuild after 'clean'