Index: cmake-3.1.0/Modules/UseSWIG.cmake
===================================================================
--- cmake-3.1.0.orig/Modules/UseSWIG.cmake
+++ cmake-3.1.0/Modules/UseSWIG.cmake
@@ -260,7 +260,7 @@ macro(SWIG_ADD_MODULE name language)
     set_target_properties(${SWIG_MODULE_${name}_REAL_NAME} PROPERTIES PREFIX "")
   elseif ("${swig_lowercase_language}" STREQUAL "python")
     # this is only needed for the python case where a _modulename.so is generated
-    set_target_properties(${SWIG_MODULE_${name}_REAL_NAME} PROPERTIES PREFIX "")
+    set_target_properties(${SWIG_MODULE_${name}_REAL_NAME} PROPERTIES PREFIX "_")
     # Python extension modules on Windows must have the extension ".pyd"
     # instead of ".dll" as of Python 2.5.  Older python versions do support
     # this suffix.