--- a/include/xplc/module.h
+++ b/include/xplc/module.h
@@ -100,19 +100,19 @@
    * XPLC module magic number. This is to ensure that it is in fact a
    * valid XPLC module that has been loaded.
    */
-  unsigned long magic;
+  signed long magic;
   /**
    * The XPLC module ABI version that this module conforms to. This
    * should always be the first member of the XPLC_ModuleInfo
    * structure, as the meaning of the following members depend on it.
    */
-  unsigned int version_major;
+  signed int version_major;
   /**
    * The XPLC module ABI sub-version that this module conforms
    * to. This is used for optional and backward-compatible changes in
    * the module ABI.
    */
-  unsigned int version_minor;
+  signed int version_minor;
 
   /**
    * Description string for the module.