diff --git a/CMakeLists.txt b/CMakeLists.txt
index 3e52c3fa1..e4953b564 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -56,7 +56,7 @@ endif()
 
 project(CALAMARES VERSION ${CALAMARES_VERSION} LANGUAGES C CXX HOMEPAGE_URL "https://calamares.io/")
 
-if(CALAMARES_RELEASE_MODE AND CMAKE_SOURCE_DIR STREQUAL CMAKE_BINARY_DIR)
+if(NOT CALAMARES_RELEASE_MODE AND CMAKE_SOURCE_DIR STREQUAL CMAKE_BINARY_DIR)
     message(FATAL_ERROR "Do not build development versions in the source-directory.")
 endif()