diff --git a/CMakeLists.txt b/CMakeLists.txt
index 7192fd0..256f256 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -47,13 +47,13 @@ pkg_check_modules(LIBPROCPS libprocps)
 pkg_check_modules(LIBPROC2 libproc2)
 
 if (LIBPROCPS_FOUND)
-    add_compile_definitions(USE_OLD_PID_VAL=false)
+    add_compile_definitions(USE_OLD_PID_VAL=0)
 elseif (LIBPROC2_FOUND)
     if (LIBPROC2_VERSION VERSION_GREATER_EQUAL "4.0.5")
-        add_compile_definitions(USE_OLD_PID_VAL=false)
+        add_compile_definitions(USE_OLD_PID_VAL=0)
+    else()
+        add_compile_definitions(USE_OLD_PID_VAL=1)
     endif()
-
-    add_compile_definitions(USE_OLD_PID_VAL=true)
 else()
     message(FATAL_ERROR "Either libprocps or libproc2 is required")
 endif()