diff --git a/Makefile b/Makefile
index a4a56d8d84..7924d2feb4 100644
--- a/Makefile
+++ b/Makefile
@@ -10,11 +10,11 @@ build: $(all)
 # We bypass cabal, and only run the main ghc --make command for a
 # fast development built. Note: Does not rebuild C libraries.
 fast: dist/caballog
-	$$(grep 'ghc --make' dist/caballog | head -n 1 | sed 's/ -O / /')
+	$$(grep 'ghc --make' dist/caballog | head -n 1)
 	ln -sf dist/build/git-annex/git-annex git-annex
 
 dist/caballog:
-	cabal configure -f-Production
+	cabal configure -f"-Production Fast"
 	cabal build -v2 | tee $@
 
 Build/SysConfig.hs: configure.hs Build/TestConfig.hs Build/Configure.hs
diff --git a/git-annex.cabal b/git-annex.cabal
index 7d370d34fc..0963731131 100644
--- a/git-annex.cabal
+++ b/git-annex.cabal
@@ -55,6 +55,9 @@ Flag DNS
 Flag Production
   Description: Enable production build (slower build; faster binary)
 
+Flag Fast
+  Description: Faster build; slower binary
+
 Flag Android
   Description: Building for Android
   Default: False
@@ -81,6 +84,9 @@ Executable git-annex
   if flag(Production)
     GHC-Options: -O2
 
+  if flag(Fast)
+    GHC-Options: -O0
+
   if flag(TestSuite)
     Build-Depends: testpack, HUnit
     CPP-Options: -DWITH_TESTSUITE