diff --git a/userspace/libsinsp/CMakeLists.txt b/userspace/libsinsp/CMakeLists.txt
index e2f7dae723..19920660e0 100644
--- a/userspace/libsinsp/CMakeLists.txt
+++ b/userspace/libsinsp/CMakeLists.txt
@@ -29,6 +29,9 @@ if(NOT MSVC)
 	endif()
 	add_definitions(-DHAVE_PWD_H)
 	add_definitions(-DHAVE_GRP_H)
+	if(MUSL_OPTIMIZED_BUILD)
+		add_definitions(-DMUSL_OPTIMIZED)
+	endif()
 endif()
 
 if(NOT DEFINED CHISEL_TOOL_LIBRARY_NAME)
diff --git a/userspace/libsinsp/test/user.ut.cpp b/userspace/libsinsp/test/user.ut.cpp
index 07dd039855..1a14e7b726 100644
--- a/userspace/libsinsp/test/user.ut.cpp
+++ b/userspace/libsinsp/test/user.ut.cpp
@@ -169,12 +169,12 @@ class usergroup_manager_host_root_test : public sinsp_with_test_input
 
 		{
 			std::ofstream ofs(etc + "/passwd");
-			ofs << "toor:x:0:0:toor:/toor:/bin/ash";
+			ofs << "toor:x:0:0:toor:/toor:/bin/ash" << std::endl;
 			ofs.close();
 		}
 		{
 			std::ofstream ofs(etc + "/group");
-			ofs << "toor:x:0:toor";
+			ofs << "toor:x:0:toor" << std::endl;
 			ofs.close();
 		}
 	}
diff --git a/userspace/libsinsp/user.cpp b/userspace/libsinsp/user.cpp
index e109fe9601..acdf3fd427 100644
--- a/userspace/libsinsp/user.cpp
+++ b/userspace/libsinsp/user.cpp
@@ -38,7 +38,7 @@ limitations under the License.
 // See fgetpwent() / fgetgrent() feature test macros:
 // https://man7.org/linux/man-pages/man3/fgetpwent.3.html
 // https://man7.org/linux/man-pages/man3/fgetgrent.3.html
-#if defined _DEFAULT_SOURCE || defined _SVID_SOURCE
+#if defined(MUSL_OPTIMIZED) || defined(_DEFAULT_SOURCE) || defined(_SVID_SOURCE)
 #define HAVE_FGET__ENT
 #endif