diff --git a/proc/pids.c b/proc/pids.c
index 4ac4efe5..50b27d27 100644
--- a/proc/pids.c
+++ b/proc/pids.c
@@ -1139,6 +1139,16 @@ PROCPS_EXPORT int procps_pids_new (
             failed = 1;
         }
     }
+    if (PIDS_SELECT_PID != PROC_PID) {
+        fprintf(stderr, "%s: header error: PIDS_SELECT_PID = 0x%04x, PROC_PID = 0x%04x\n"
+            , __FILE__, PIDS_SELECT_PID, PROC_PID);
+        failed = 1;
+    }
+    if (PIDS_SELECT_UID != PROC_UID) {
+        fprintf(stderr, "%s: header error: PIDS_SELECT_UID = 0x%04x, PROC_UID = 0x%04x\n"
+            , __FILE__, PIDS_SELECT_UID, PROC_UID);
+        failed = 1;
+    }
     if (failed) _Exit(EXIT_FAILURE);
 #endif
 
diff --git a/proc/readproc.h b/proc/readproc.h
index 576fed4f..fea120a6 100644
--- a/proc/readproc.h
+++ b/proc/readproc.h
@@ -220,6 +220,7 @@ typedef struct PROCTAB {
 // consider only processes with one of the passed:
 #define PROC_PID             0x1000  // process id numbers ( 0   terminated)
 #define PROC_UID             0x4000  // user id numbers    ( length needed )
+// Note: the above 2 values must NOT change without also changing pids.h !!!
 
 #define PROC_EDITCGRPCVT    0x10000 // edit `cgroup' as regular string
 #define PROC_EDITCMDLCVT    0x20000 // edit `cmdline' as regular string