diff --git a/CMakeLists.txt b/CMakeLists.txt
index ef436da..0179b44 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,4 +1,4 @@
-if (CMAKE_BINARY_DIR STREQUAL CMAKE_SOURCE_DIR)
+if (CMAKE_BINARY_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR)
     message(FATAL_ERROR "In-tree builds are not supported. Instead, run:\ncmake . -B build <options> && cmake --build build")
 endif()
 
@@ -11,7 +11,7 @@ set(CMAKE_CXX_STANDARD_REQUIRED ON)
 set(CMAKE_CXX_EXTENSIONS OFF)
 
 project(yosys-slang CXX)
-set(CMAKE_MODULE_PATH "${CMAKE_SOURCE_DIR}/cmake" ${CMAKE_MODULE_PATH})
+set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${CMAKE_CURRENT_SOURCE_DIR}/cmake")
 
 option(BUILD_AS_PLUGIN "Build yosys-slang as a plugin" ON)
 mark_as_advanced(BUILD_AS_PLUGIN)
@@ -51,7 +51,7 @@ option(FMT_INSTALL OFF)
 FetchContent_Declare(
     fmt
     EXCLUDE_FROM_ALL
-    SOURCE_DIR ${CMAKE_SOURCE_DIR}/third_party/fmt
+    SOURCE_DIR ${CMAKE_CURRENT_SOURCE_DIR}/third_party/fmt
 )
 
 set(SLANG_USE_MIMALLOC OFF)
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 79d5baa..c58d263 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -1,8 +1,8 @@
 find_package(Yosys)
 include(GitRevision)
 
-git_rev_parse(YOSYS_SLANG_REVISION ${CMAKE_SOURCE_DIR})
-git_rev_parse(SLANG_REVISION ${CMAKE_SOURCE_DIR}/third_party/slang)
+git_rev_parse(YOSYS_SLANG_REVISION ${CMAKE_CURRENT_SOURCE_DIR}/..)
+git_rev_parse(SLANG_REVISION ${CMAKE_CURRENT_SOURCE_DIR}/../third_party/slang)
 configure_file(${CMAKE_CURRENT_SOURCE_DIR}/version.h.in ${CMAKE_CURRENT_BINARY_DIR}/version.h)
 
 if (BUILD_AS_PLUGIN)