diff --git a/utils/libmarias3/CMakeLists.txt b/utils/libmarias3/CMakeLists.txt
index 609bbe652..dd9a63e62 100644
--- a/utils/libmarias3/CMakeLists.txt
+++ b/utils/libmarias3/CMakeLists.txt
@@ -14,6 +14,7 @@ ADD_LIBRARY(marias3 SHARED ${S3_SOURCES})
 
 TARGET_LINK_LIBRARIES(marias3 curl)
 INCLUDE_DIRECTORIES(${CMAKE_CURRENT_SOURCE_DIR} ${S3API_DIR})
+add_definitions(-D_GNU_SOURCE)
 
 set(S3API_DEPS marias3 curl CACHE INTERNAL "S3API_DEPS")