--- include/pub_tool_basics.h.orig
+++ include/pub_tool_basics.h
@@ -102,7 +102,7 @@
 // always a signed 64-bit int.  So we defined our own Off64T as well.
 #if defined(VGO_linux) || defined(VGO_solaris)
 typedef Word                   OffT;      // 32             64
-#elif defined(VGO_freebsd)
+#elif defined(VGO_freebsd) || defined(VGO_openbsd)
 typedef Long                   OffT;      // 64             64
 #elif defined(VGO_darwin)
 typedef Long                   OffT;      // 64             64
@@ -227,7 +227,7 @@
       SysResMode _mode;
    }
    SysRes;
-#elif defined(VGO_freebsd)
+#elif defined(VGO_freebsd) || defined(VGO_openbsd)
 typedef
    struct {
       UWord _val;
@@ -235,8 +235,8 @@
       Bool  _isError;
 #if defined(VGP_amd64_freebsd)
       char  padding[7];
-#else
-      char  padding[3];
+#elif defined(VGO_openbsd)
+      Bool  _hasVal2;
 #endif
    }
    SysRes;
@@ -321,7 +321,7 @@
           && sr1._isError == sr2._isError;
 }
 
-#elif defined(VGO_freebsd)
+#elif defined(VGO_freebsd) || defined(VGO_openbsd)
 
 static inline Bool sr_isError ( SysRes sr ) {
    return sr._isError;