diff --git a/src/tool_writeout.c b/src/tool_writeout.c
index 6ff45b9be295d7..6879a98c264d7b 100644
--- a/src/tool_writeout.c
+++ b/src/tool_writeout.c
@@ -57,14 +57,17 @@ static const char *http_version[] = {
    with exceptions special cased in the respective function. For example,
    http_version uses CURLINFO_HTTP_VERSION which returns the version as a long,
    however it is output as a string and therefore is handled in writeString.
+
    Yes: "http_version": "1.1"
    No:  "http_version": 1.1
+
+   Variable names should be in alphabetical order.
    */
 static const struct writeoutvar variables[] = {
   {"content_type", VAR_CONTENT_TYPE, 0, CURLINFO_CONTENT_TYPE, writeString},
-  {"filename_effective", VAR_EFFECTIVE_FILENAME, 0, 0, writeString},
-  {"exitcode", VAR_EXITCODE, 0, 0, writeLong},
   {"errormsg", VAR_ERRORMSG, 0, 0, writeString},
+  {"exitcode", VAR_EXITCODE, 0, 0, writeLong},
+  {"filename_effective", VAR_EFFECTIVE_FILENAME, 0, 0, writeString},
   {"ftp_entry_path", VAR_FTP_ENTRY_PATH, 0, CURLINFO_FTP_ENTRY_PATH,
    writeString},
   {"http_code", VAR_HTTP_CODE, 0, CURLINFO_RESPONSE_CODE, writeLong},
@@ -111,7 +114,7 @@ static const struct writeoutvar variables[] = {
   {"time_total", VAR_TOTAL_TIME, 0, CURLINFO_TOTAL_TIME_T, writeTime},
   {"url", VAR_INPUT_URL, 0, 0, writeString},
   {"url_effective", VAR_EFFECTIVE_URL, 0, CURLINFO_EFFECTIVE_URL, writeString},
-  {"urlnum", VAR_URLNUM, 0, 0, writeOffset},
+  {"urlnum", VAR_URLNUM, 0, 0, writeLong},
   {NULL, VAR_NONE, 1, 0, NULL}
 };
 
@@ -120,23 +123,37 @@ static int writeTime(FILE *stream, const struct writeoutvar *wovar,
                      struct per_transfer *per, CURLcode per_result,
                      bool use_json)
 {
+  bool valid = false;
   curl_off_t us = 0;
+
   (void)per;
   (void)per_result;
-  DEBUGASSERT(wovar->writefunc == writeTime);
-  if(use_json)
-    fprintf(stream, "\"%s\":", wovar->name);
-  if(!curl_easy_getinfo(per->curl, wovar->ci, &us)) {
+  DEBUGASSERT(wovar->is_ctrl == 0 && wovar->writefunc == writeTime);
+
+  if(wovar->ci) {
+    if(!curl_easy_getinfo(per->curl, wovar->ci, &us))
+      valid = true;
+  }
+  else {
+    DEBUGASSERT(0);
+  }
+
+  if(valid) {
     curl_off_t secs = us / 1000000;
     us %= 1000000;
+
+    if(use_json)
+      fprintf(stream, "\"%s\":", wovar->name);
+
     fprintf(stream, "%" CURL_FORMAT_CURL_OFF_TU
             ".%06" CURL_FORMAT_CURL_OFF_TU, secs, us);
   }
   else {
     if(use_json)
-      fprintf(stream, "null");
+      fprintf(stream, "\"%s\":null", wovar->name);
   }
-  return 1;
+
+  return 1; /* return 1 if anything was written */
 }
 
 /* write functions must return 1 if anything was written */
@@ -144,19 +161,25 @@ static int writeString(FILE *stream, const struct writeoutvar *wovar,
                        struct per_transfer *per, CURLcode per_result,
                        bool use_json)
 {
+  bool valid = false;
   const char *strinfo = NULL;
-  DEBUGASSERT(wovar->writefunc == writeString);
-  if(wovar->ci == CURLINFO_HTTP_VERSION) {
-    long version = 0;
-    if(!curl_easy_getinfo(per->curl, CURLINFO_HTTP_VERSION, &version) &&
-       (version >= 0) &&
-       (version < (long)(sizeof(http_version)/sizeof(http_version[0])))) {
-      strinfo = http_version[version];
+
+  DEBUGASSERT(wovar->is_ctrl == 0 && wovar->writefunc == writeString);
+
+  if(wovar->ci) {
+    if(wovar->ci == CURLINFO_HTTP_VERSION) {
+      long version = 0;
+      if(!curl_easy_getinfo(per->curl, CURLINFO_HTTP_VERSION, &version) &&
+         (version >= 0) &&
+         (version < (long)(sizeof(http_version)/sizeof(http_version[0])))) {
+        strinfo = http_version[version];
+        valid = true;
+      }
+    }
+    else {
+      if(!curl_easy_getinfo(per->curl, wovar->ci, &strinfo) && strinfo)
+        valid = true;
     }
-  }
-  else if(wovar->ci) {
-    if(curl_easy_getinfo(per->curl, wovar->ci, &strinfo))
-      strinfo = NULL;
   }
   else {
     switch(wovar->id) {
@@ -164,31 +187,38 @@ static int writeString(FILE *stream, const struct writeoutvar *wovar,
       if(per_result) {
         strinfo = per->errorbuffer[0] ? per->errorbuffer :
                   curl_easy_strerror(per_result);
+        valid = true;
       }
       break;
     case VAR_EFFECTIVE_FILENAME:
       strinfo = per->outs.filename;
+      valid = true;
       break;
     case VAR_INPUT_URL:
       strinfo = per->this_url;
+      valid = true;
       break;
     default:
-      return 0;
+      DEBUGASSERT(0);
+      break;
     }
   }
-  if(use_json) {
-    fprintf(stream, "\"%s\":", wovar->name);
-    if(strinfo) {
-      fprintf(stream, "\"");
+
+  if(valid) {
+    if(use_json) {
+      fprintf(stream, "\"%s\":\"", wovar->name);
       jsonWriteString(stream, strinfo);
-      fprintf(stream, "\"");
+      fputs("\"", stream);
     }
     else
-      fprintf(stream, "null");
+      fputs(strinfo, stream);
+  }
+  else {
+    if(use_json)
+      fprintf(stream, "\"%s\":null", wovar->name);
   }
-  else
-    fputs(strinfo, stream);
-  return 1;
+
+  return 1; /* return 1 if anything was written */
 }
 
 /* write functions must return 1 if anything was written */
@@ -196,53 +226,85 @@ static int writeLong(FILE *stream, const struct writeoutvar *wovar,
                      struct per_transfer *per, CURLcode per_result,
                      bool use_json)
 {
+  bool valid = false;
   long longinfo = 0;
-  DEBUGASSERT(wovar->writefunc == writeLong);
+
+  DEBUGASSERT(wovar->is_ctrl == 0 && wovar->writefunc == writeLong);
+
   if(wovar->ci) {
-    curl_easy_getinfo(per->curl, wovar->ci, &longinfo);
+    if(!curl_easy_getinfo(per->curl, wovar->ci, &longinfo))
+      valid = true;
   }
   else {
     switch(wovar->id) {
     case VAR_NUM_HEADERS:
       longinfo = per->num_headers;
+      valid = true;
       break;
     case VAR_EXITCODE:
       longinfo = per_result;
+      valid = true;
       break;
     case VAR_URLNUM:
-      if(per->urlnum > LONG_MAX)
-        return 0;
-      longinfo = (long)per->urlnum;
+      if(per->urlnum <= LONG_MAX) {
+        longinfo = (long)per->urlnum;
+        valid = true;
+      }
+      break;
     default:
-      return 0;
+      DEBUGASSERT(0);
+      break;
     }
   }
-  if(use_json)
-    fprintf(stream, "\"%s\":", wovar->name);
-
-  if(wovar->id == VAR_HTTP_CODE || wovar->id == VAR_HTTP_CODE_PROXY)
-    fprintf(stream, "%03ld", longinfo);
-  else
-    fprintf(stream, "%ld", longinfo);
-  return 1;
+
+  if(valid) {
+    if(use_json)
+      fprintf(stream, "\"%s\":", wovar->name);
+
+    if(wovar->id == VAR_HTTP_CODE || wovar->id == VAR_HTTP_CODE_PROXY)
+      fprintf(stream, "%03ld", longinfo);
+    else
+      fprintf(stream, "%ld", longinfo);
+  }
+  else {
+    if(use_json)
+      fprintf(stream, "\"%s\":null", wovar->name);
+  }
+
+  return 1; /* return 1 if anything was written */
 }
 
-/* write functions must return 1 if anything was written */
 static int writeOffset(FILE *stream, const struct writeoutvar *wovar,
                        struct per_transfer *per, CURLcode per_result,
                        bool use_json)
 {
+  bool valid = false;
   curl_off_t offinfo = 0;
+
   (void)per;
   (void)per_result;
-  DEBUGASSERT(wovar->writefunc == writeOffset);
-  if(wovar->ci && !curl_easy_getinfo(per->curl, wovar->ci, &offinfo)) {
+  DEBUGASSERT(wovar->is_ctrl == 0 && wovar->writefunc == writeOffset);
+
+  if(wovar->ci) {
+    if(!curl_easy_getinfo(per->curl, wovar->ci, &offinfo))
+      valid = true;
+  }
+  else {
+    DEBUGASSERT(0);
+  }
+
+  if(valid) {
     if(use_json)
       fprintf(stream, "\"%s\":", wovar->name);
+
     fprintf(stream, "%" CURL_FORMAT_CURL_OFF_T, offinfo);
-    return 1;
   }
-  return 0;
+  else {
+    if(use_json)
+      fprintf(stream, "\"%s\":null", wovar->name);
+  }
+
+  return 1; /* return 1 if anything was written */
 }
 
 void ourWriteOut(const char *writeinfo, struct per_transfer *per,
@@ -293,8 +355,8 @@ void ourWriteOut(const char *writeinfo, struct per_transfer *per,
                 ourWriteOutJSON(stream, variables, per, per_result);
                 break;
               default:
-                variables[i].writefunc(stream, &variables[i], per, per_result,
-                                       false);
+                (void)variables[i].writefunc(stream, &variables[i],
+                                             per, per_result, false);
                 break;
               }
               break;
diff --git a/src/tool_writeout_json.c b/src/tool_writeout_json.c
index b4e53d9bc2305a..f8f38146ee94b6 100644
--- a/src/tool_writeout_json.c
+++ b/src/tool_writeout_json.c
@@ -76,19 +76,16 @@ void ourWriteOutJSON(FILE *stream, const struct writeoutvar mappings[],
   int i;
 
   fputs("{", stream);
-  for(i = 0; mappings[i].name != NULL; i++) {
-    int ok = 0;
 
-    if(mappings[i].is_ctrl == 1)
+  for(i = 0; mappings[i].name != NULL; i++) {
+    if(mappings[i].is_ctrl)
       continue;
-
-    ok = mappings[i].writefunc(stream, &mappings[i], per, per_result, true);
-
-    if(ok) {
+    if(mappings[i].writefunc(stream, &mappings[i], per, per_result, true))
       fputs(",", stream);
-    }
   }
 
+  /* The variables are sorted in alphabetical order but as a special case
+     curl_version (which is not actually a --write-out variable) is last. */
   fprintf(stream, "\"curl_version\":\"");
   jsonWriteString(stream, curl_version());
   fprintf(stream, "\"}");