diff --git a/src/alire-os_lib.adb b/src/alire-os_lib.adb
index c7217d2e..d2dee59a 100644
--- a/src/alire-os_lib.adb
+++ b/src/alire-os_lib.adb
@@ -25,7 +25,7 @@ package body Alire.OS_Lib is
    -----------
    -- FIXME: memory leaks
    function Spawn (Command   : String;
-                   Arguments : String) return Integer is
+                   Arguments : String := "") return Integer is
    begin
       Log ("Spawning: " & Command & " " & Arguments, Verbose);
       return
@@ -38,7 +38,7 @@ package body Alire.OS_Lib is
    -----------
 
    procedure Spawn (Command   : String;
-                    Arguments : String)
+                    Arguments : String := "")
    is
       Code : constant Integer := Spawn (Command, Arguments);
    begin
diff --git a/src/alire-os_lib.ads b/src/alire-os_lib.ads
index 22728b78..02fec614 100644
--- a/src/alire-os_lib.ads
+++ b/src/alire-os_lib.ads
@@ -4,11 +4,11 @@ with Ada.Finalization;
 package Alire.OS_Lib is
 
    function Spawn (Command   : String; 
-                   Arguments : String) return Integer;
+                   Arguments : String := "") return Integer;
    --  Returns exit code
    
    procedure Spawn (Command   : String; 
-                    Arguments : String);
+                    Arguments : String:= "");
    --  Raises PROGRAM_ERROR if exit code /= 0   
    
    type Folder_Guard (<>) is limited private;
diff --git a/src/alire-query.adb b/src/alire-query.adb
index 392c4bf2..d10e72bd 100644
--- a/src/alire-query.adb
+++ b/src/alire-query.adb
@@ -40,7 +40,8 @@ package body Alire.Query is
    -------------
 
    function Resolve (Unresolved : Dependencies;
-                     Frozen     : Instance) return Instance
+                     Frozen     : Instance;
+                     Success    : out Boolean) return Instance
    is
    --  FIXME: since this is depth-first, Frozen can be passed in-out and updated on the spot,
    --  thus saving copies. Probably the same applies to Unresolved.
@@ -60,11 +61,12 @@ package body Alire.Query is
             Print_Solution (Frozen);
             return Frozen;
          else
-            return Resolve (Unresolved, Frozen);
+            return Resolve (Unresolved, Frozen, Success);
          end if;
       end Go_Deeper;
 
    begin
+
       Remain.Delete_First;
 
       if Frozen.Contains (Dep.Project) then
@@ -92,6 +94,7 @@ package body Alire.Query is
                   Solution := Go_Deeper (New_Remain, New_Frozen);
 
                   if not Solution.Is_Empty then
+                     Success := True;
                      return Solution; -- Success!
                   end if;
                end;
@@ -107,9 +110,12 @@ package body Alire.Query is
    -- Resolve --
    -------------
 
-   function Resolve (Deps : Dependencies) return Instance is
+   function Resolve (Deps    : Dependencies;
+                     Success : out Boolean) return Instance is
    begin
-      return Resolve (Deps, Containers.Project_Release_Maps.Empty_Map);
+      Success := False;
+
+      return Resolve (Deps, Containers.Project_Release_Maps.Empty_Map, Success);
    end Resolve;
 
 end Alire.Query;
diff --git a/src/alire-query.ads b/src/alire-query.ads
index d1cf71b9..ad2e5cc4 100644
--- a/src/alire-query.ads
+++ b/src/alire-query.ads
@@ -4,7 +4,8 @@ package Alire.Query is
    
    function Exists (Project : Project_Name) return Boolean;
 
-   function Resolve (Deps : Dependencies) return Instance;        
+   function Resolve (Deps : Dependencies;
+                     Success    : out Boolean) return Instance;        
    
    procedure Print_Solution (I : Instance);
 
diff --git a/src/alire.adb b/src/alire.adb
index 24e3e123..fecc2928 100644
--- a/src/alire.adb
+++ b/src/alire.adb
@@ -8,8 +8,8 @@ package body Alire is
          GNAT.IO.Put_Line
            ((case Level is
                when Terse => "",
-               when Verbose => ": ",
-               when Debug   => "+++ ") & S);
+               when Verbose => "> ",
+               when Debug   => ">> ") & S);
       end if;
    end Log;