diff --git a/CMakeLists.txt b/CMakeLists.txt
index b676edd..fd908b0 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -72,6 +72,9 @@ elseif(CMAKE_SYSTEM_NAME MATCHES "OpenBSD")
   message(STATUS "OpenBSD detected")
   message(WARNING "OpenBSD is still experimental!")
   set(METER_SOURCES "openbsd/memory.cc" "openbsd/cpu.cc" "openbsd/load.cc")
+  if(CMAKE_SYSTEM_VERSION VERSION_LESS 5.7)
+    add_definitions(-DOPENBSD_WORKAROUND=1)
+  endif()
 else()
   message(FATAL_ERROR "Cannot be compiled on this system")
 endif()
diff --git a/openbsd/memory.cc b/openbsd/memory.cc
index 5724303..832cbbf 100644
--- a/openbsd/memory.cc
+++ b/openbsd/memory.cc
@@ -18,9 +18,22 @@
 
 #include <sstream>
 #include <string>
+
+// Ugly fix to compilation on OpenBSD 5.6
+// these need to be before include sys/mount.h
+// and be in this exact order. Otherwise compiling on
+// OpenBSD 5.6 will fail with missing NGROUPS define
+// or missing gid_t typedefs
+#ifdef OPENBSD_WORKAROUND
+#include <sys/types.h> // typedefs
+#include <sys/param.h> // missing NGROUPS
+#include <sys/ucred.h>
+#else
+#include <sys/types.h>
+#endif
+
 #include <sys/mount.h> // VFS_* which we use to get cache
 #include <sys/sysctl.h>
-#include <sys/types.h>
 #include <sys/vmmeter.h> // vmtotal struct
 
 #include "error.h"