diff --git a/lib/gollum/committer.rb b/lib/gollum/committer.rb
index 3a1e13da..719c1a95 100644
--- a/lib/gollum/committer.rb
+++ b/lib/gollum/committer.rb
@@ -85,6 +85,10 @@ module Gollum
     #
     # Returns nothing (modifies the Index in place).
     def add_to_index(dir, name, format, data, allow_same_ext = false)
+      # spaces must be dashes
+      dir.gsub!(' ', '-')
+      name.gsub!(' ', '-')
+
       path = @wiki.page_file_name(name, format)
 
       dir = '/' if dir.strip.empty?
diff --git a/lib/gollum/wiki.rb b/lib/gollum/wiki.rb
index 51d505f6..fe1c847c 100644
--- a/lib/gollum/wiki.rb
+++ b/lib/gollum/wiki.rb
@@ -287,6 +287,10 @@ module Gollum
     # Returns the String SHA1 of the newly written version, or the
     # Gollum::Committer instance if this is part of a batch update.
     def write_page(name, format, data, commit = {}, dir = '')
+      # spaces must be dashes
+      name.gsub!(' ', '-')
+      dir.gsub!(' ', '-')
+
       multi_commit = false
 
       committer = if obj = commit[:committer]