diff --git a/spec/config-spec.coffee b/spec/config-spec.coffee
index 7b7c94c1d..0156855d9 100644
--- a/spec/config-spec.coffee
+++ b/spec/config-spec.coffee
@@ -193,8 +193,14 @@ describe "Config", ->
       atom.config.unset('a.c')
       expect(atom.config.save.callCount).toBe 1
 
-    it "throws when called with a source but no scope", ->
-      expect(-> atom.config.unset("a.b", source: "the-source")).toThrow()
+    describe "when a 'source' and no 'scopeSelector' is given", ->
+      it "removes all scoped settings with the given source", ->
+        atom.config.set("foo.bar.baz", 1, scopeSelector: ".a", source: "source-a")
+        atom.config.set("foo.bar.quux", 2, scopeSelector: ".b", source: "source-a")
+        expect(atom.config.get("foo.bar", scope: [".a.b"])).toEqual(baz: 1, quux: 2)
+
+        atom.config.unset(null, source: "source-a")
+        expect(atom.config.get("foo.bar", scope: [".a"])).toEqual(baz: 0, ok: 0)
 
     describe "when a 'scopeSelector' is given", ->
       it "restores the global default when no scoped default set", ->
diff --git a/src/config.coffee b/src/config.coffee
index 4931994ab..8169b13f2 100644
--- a/src/config.coffee
+++ b/src/config.coffee
@@ -585,9 +585,6 @@ class Config
     else
       {scopeSelector, source} = options ? {}
 
-    if source and not scopeSelector
-      throw new Error("::unset with a 'source' and no 'sourceSelector' is not yet implemented!")
-
     source ?= @getUserConfigPath()
 
     if scopeSelector?
@@ -603,7 +600,10 @@ class Config
         @scopedSettingsStore.removePropertiesForSource(source)
         @emitChangeEvent()
     else
-      @set(keyPath, _.valueForKeyPath(@defaultSettings, keyPath))
+      @scopedSettingsStore.removePropertiesForSource(source)
+      if keyPath?
+        @set(keyPath, _.valueForKeyPath(@defaultSettings, keyPath))
+
 
   # Extended: Get an {Array} of all of the `source` {String}s with which
   # settings have been added via {::set}.