diff --git a/kill.c b/kill.c
index bf51b7d..d4746f7 100644
--- a/kill.c
+++ b/kill.c
@@ -391,6 +391,8 @@ bool is_larger(const poll_loop_args_t* args, const procinfo_t* victim, procinfo_
     return true;
 }
 
+// Fill the fields in `cur` that are not required for the kill decision.
+// Used to log details about the selected process.
 void fill_informative_fields(procinfo_t* cur)
 {
     if (strlen(cur->name) == 0) {
@@ -440,13 +442,12 @@ procinfo_t find_largest_process(const poll_loop_args_t* args)
 
     debug_print_procinfo_header();
 
-    const int field_not_set = -9999; // placeholder value
     const procinfo_t empty_procinfo = {
-        .pid = field_not_set,
-        .uid = field_not_set,
-        .badness = field_not_set,
-        .oom_score_adj = field_not_set,
-        .VmRSSkiB = field_not_set,
+        .pid = PROCINFO_FIELD_NOT_SET,
+        .uid = PROCINFO_FIELD_NOT_SET,
+        .badness = PROCINFO_FIELD_NOT_SET,
+        .oom_score_adj = PROCINFO_FIELD_NOT_SET,
+        .VmRSSkiB = PROCINFO_FIELD_NOT_SET,
         /* omitted fields are set to zero */
     };
 
diff --git a/meminfo.h b/meminfo.h
index 7dd1b22..cf7945c 100644
--- a/meminfo.h
+++ b/meminfo.h
@@ -4,8 +4,8 @@
 
 #define PATH_LEN 256
 
-#include <stdbool.h>
 #include "proc_pid.h"
+#include <stdbool.h>
 
 typedef struct {
     // Values from /proc/meminfo, in KiB
@@ -34,6 +34,9 @@ typedef struct procinfo {
     char cmdline[PATH_LEN];
 } procinfo_t;
 
+// placeholder value for numeric fields
+#define PROCINFO_FIELD_NOT_SET -9999
+
 meminfo_t parse_meminfo();
 bool is_alive(int pid);
 void print_mem_stats(int (*out_func)(const char* fmt, ...), const meminfo_t m);
diff --git a/proc_pid.h b/proc_pid.h
index 97122e1..dbef9d4 100644
--- a/proc_pid.h
+++ b/proc_pid.h
@@ -2,6 +2,8 @@
 #ifndef PROC_PID_H
 #define PROC_PID_H
 
+#include <stdbool.h>
+
 typedef struct {
     char state;
     int ppid;