diff --git a/pkgs/development/interpreters/python/2.6/default.nix b/pkgs/development/interpreters/python/2.6/default.nix
index ffc4c5d2e1f..10c52e958d8 100644
--- a/pkgs/development/interpreters/python/2.6/default.nix
+++ b/pkgs/development/interpreters/python/2.6/default.nix
@@ -144,6 +144,7 @@ let
             'self.extensions = [ext for ext in self.extensions if ext.name in ["${internalName}"]]'
 
           python ./setup.py build_ext
+          [ -z "$(find build -name '*_failed.so' -print)" ]
         '';
 
       installPhase =
diff --git a/pkgs/development/interpreters/python/2.7/default.nix b/pkgs/development/interpreters/python/2.7/default.nix
index b8b25c576c5..e9d9dc6824d 100644
--- a/pkgs/development/interpreters/python/2.7/default.nix
+++ b/pkgs/development/interpreters/python/2.7/default.nix
@@ -161,6 +161,7 @@ let
             'self.extensions = [ext for ext in self.extensions if ext.name in ["${internalName}"]]'
 
           python ./setup.py build_ext
+          [ -z "$(find build -name '*_failed.so' -print)" ]
         '';
 
       installPhase =