diff --git a/AUTHORS b/AUTHORS
index 6dbdd94..87df086 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -25,3 +25,4 @@ Shakeel Mohamed (https://github.com/shakeelmohamed)
 Denis Izmaylov (https://github.com/DenisIzmaylov)
 Guillermo Grau Panea (https://github.com/guigrpa)
 Mark LeMerise (https://github.com/MarkLeMerise)
+https://github.com/sometimesalready
diff --git a/CHANGES.md b/CHANGES.md
index 5111e9a..9178fe8 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -8,7 +8,12 @@ Known issues:
 
 ## 1.5.2 (not yet released)
 
-(nothing yet)
+- [issue #325] Allow one to set `level: 0` in `createLogger` to turn on
+  logging for all levels. (Adapted from #336 by github.com/sometimesalready.)
+
+- Add guards (to `resolveLevel`) so that all "level" values are validated.
+  Before this, a bogus level like "foo" or -12 or `['some', 'array']` would
+  silently be accepted -- with undefined results.
 
 
 ## 1.5.1
diff --git a/lib/bunyan.js b/lib/bunyan.js
index 97d2d47..bda7006 100644
--- a/lib/bunyan.js
+++ b/lib/bunyan.js
@@ -248,12 +248,27 @@ var probes = dtrace && {};
 /**
  * Resolve a level number, name (upper or lowercase) to a level number value.
  *
+ * @param nameOrNum {String|Number} A level name (case-insensitive) or positive
+ *      integer level.
  * @api public
  */
 function resolveLevel(nameOrNum) {
-    var level = (typeof (nameOrNum) === 'string'
-            ? levelFromName[nameOrNum.toLowerCase()]
-            : nameOrNum);
+    var level;
+    var type = typeof (nameOrNum);
+    if (type === 'string') {
+        level = levelFromName[nameOrNum.toLowerCase()];
+        if (!level) {
+            throw new Error(format('unknown level name: "%s"', nameOrNum));
+        }
+    } else if (type !== 'number') {
+        throw new TypeError(format('cannot resolve level: invalid arg (%s):',
+            type, nameOrNum));
+    } else if (nameOrNum < 0 || Math.floor(nameOrNum) !== nameOrNum) {
+        throw new TypeError(format('level is not a positive integer: %s',
+            nameOrNum));
+    } else {
+        level = nameOrNum;
+    }
     return level;
 }
 
@@ -513,7 +528,7 @@ Logger.prototype.addStream = function addStream(s, defaultLevel) {
     }
     s.raw = (s.type === 'raw');  // PERF: Allow for faster check in `_emit`.
 
-    if (s.level) {
+    if (s.level !== undefined) {
         s.level = resolveLevel(s.level);
     } else {
         s.level = resolveLevel(defaultLevel);
diff --git a/test/level.test.js b/test/level.test.js
index 7e6a33f..ab619f2 100644
--- a/test/level.test.js
+++ b/test/level.test.js
@@ -69,5 +69,30 @@ test('log.level(<weird numbers>)', function (t) {
     t.equal(log1.level(), 0);
     log1.level(Number.MAX_VALUE);
     t.equal(log1.level(), Number.MAX_VALUE);
+    log1.level(Infinity);
+    t.equal(log1.level(), Infinity);
+    t.end();
+});
+
+test('log.level(<invalid values>)', function (t) {
+    t.throws(function () {
+        var log = bunyan.createLogger({name: 'invalid', level: 'booga'});
+    // JSSTYLED
+    }, /unknown level name: "booga"/);
+    t.throws(function () {
+        var log = bunyan.createLogger({name: 'invalid', level: []});
+    }, /cannot resolve level: invalid arg \(object\): \[\]/);
+    t.throws(function () {
+        var log = bunyan.createLogger({name: 'invalid', level: true});
+    }, /cannot resolve level: invalid arg \(boolean\): true/);
+    t.throws(function () {
+        var log = bunyan.createLogger({name: 'invalid', level: -1});
+    }, /level is not a positive integer: -1/);
+    t.throws(function () {
+        var log = bunyan.createLogger({name: 'invalid', level: 3.14});
+    }, /level is not a positive integer: 3.14/);
+    t.throws(function () {
+        var log = bunyan.createLogger({name: 'invalid', level: -Infinity});
+    }, /level is not a positive integer: -Infinity/);
     t.end();
 });
diff --git a/test/stream-levels.test.js b/test/stream-levels.test.js
index 7e2969d..6e12e09 100644
--- a/test/stream-levels.test.js
+++ b/test/stream-levels.test.js
@@ -171,3 +171,14 @@ test('two streams, one with "level" specified', function (t) {
     t.equal(log.streams[1].level, bunyan.FATAL);
     t.end();
 });
+
+// Issue #335
+test('log level 0 to turn on all logging', function (t) {
+    var log = bunyan.createLogger({
+        name: 'foo',
+        level: 0
+    });
+    t.equal(log.level(), 0);
+    t.equal(log.streams[0].level, 0);
+    t.end();
+});