diff --git a/Library/Homebrew/utils.rb b/Library/Homebrew/utils.rb
index 8ff6e8620c..088aea1955 100644
--- a/Library/Homebrew/utils.rb
+++ b/Library/Homebrew/utils.rb
@@ -132,23 +132,24 @@ end
 
 # returns array of architectures suitable for -arch gcc flag
 def archs_for_command cmd
-    cmd = `/usr/bin/which #{cmd}` unless Pathname.new(cmd).absolute?
-    cmd.gsub! ' ', '\\ '
+  cmd = cmd.to_s # If we were passed a Pathname, turn it into a string.
+  cmd = `/usr/bin/which #{cmd}` unless Pathname.new(cmd).absolute?
+  cmd.gsub! ' ', '\\ '  # Escape spaces in the filename.
 
-    IO.popen("/usr/bin/file #{cmd}").readlines.inject(%w[]) do |archs, line|
-      case line
-      when /Mach-O executable ppc/
-        archs << :ppc7400
-      when /Mach-O 64-bit executable ppc64/
-        archs << :ppc64
-      when /Mach-O executable i386/
-        archs << :i386
-      when /Mach-O 64-bit executable x86_64/
-        archs << :x86_64
-      else
-        archs
-      end
+  IO.popen("/usr/bin/file #{cmd}").readlines.inject(%w[]) do |archs, line|
+    case line
+    when /Mach-O executable ppc/
+      archs << :ppc7400
+    when /Mach-O 64-bit executable ppc64/
+      archs << :ppc64
+    when /Mach-O executable i386/
+      archs << :i386
+    when /Mach-O 64-bit executable x86_64/
+      archs << :x86_64
+    else
+      archs
     end
+  end
 end
 
 # String extensions added by inreplace below.