diff --git a/src/svxlink/svxlink/CMakeLists.txt b/src/svxlink/svxlink/CMakeLists.txt
index 8ddd5c75..f9fb4fca 100644
--- a/src/svxlink/svxlink/CMakeLists.txt
+++ b/src/svxlink/svxlink/CMakeLists.txt
@@ -24,6 +24,7 @@ include_directories(${GSM_INCLUDE_DIR})
 
 # Include contributed parts
 add_subdirectory(contrib)
+add_definitions(${SVXLINK_DEFINES})
 
 # Find the TCL library
 if(TCL_LIBRARY)
diff --git a/src/svxlink/svxlink/contrib/CMakeLists.txt b/src/svxlink/svxlink/contrib/CMakeLists.txt
index 59b9f5cc..b1653476 100644
--- a/src/svxlink/svxlink/contrib/CMakeLists.txt
+++ b/src/svxlink/svxlink/contrib/CMakeLists.txt
@@ -1,9 +1,20 @@
-option(WITH_CONTRIB_SIP_LOGIC
+# Add a subdirectory containing contributed code
+#
+#   name - The upper case name of the contrib
+#   subdir - The subdirectory where the code is found
+#   comment - Comment text for the CMake option
+#
+macro(add_contrib name subdir comment)
+  option(WITH_CONTRIB_${name} ${comment})
+  if(${WITH_CONTRIB_${name}})
+    message(STATUS "Building experimental contributed code ${subdir}")
+    set(SVXLINK_DEFINES ${SVXLINK_DEFINES} "-DWITH_CONTRIB_${name}=ON" PARENT_SCOPE)
+    add_subdirectory(${subdir})
+  endif(${WITH_CONTRIB_${name}})
+endmacro(add_contrib)
+
+add_contrib(SIP_LOGIC SipLogic
   "Set to ON to build and install contributed logic core SipLogic")
-if(WITH_CONTRIB_SIP_LOGIC)
-  message(STATUS "Building experimental logic core SipLogic")
-  add_subdirectory(SipLogic)
-endif(WITH_CONTRIB_SIP_LOGIC)
 
 # Propagate variables upwards
 set(LIBS ${LIBS} PARENT_SCOPE)
diff --git a/src/svxlink/svxlink/svxlink.cpp b/src/svxlink/svxlink/svxlink.cpp
index 403ca530..d2ec6d4f 100644
--- a/src/svxlink/svxlink/svxlink.cpp
+++ b/src/svxlink/svxlink/svxlink.cpp
@@ -85,8 +85,8 @@ Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 #include "SimplexLogic.h"
 #include "RepeaterLogic.h"
 #include "ReflectorLogic.h"
-#ifdef PJSIP_MAJOR
-#include "SipLogic.h"
+#ifdef WITH_CONTRIB_SIP_LOGIC
+#include "contrib/SipLogic/SipLogic.h"
 #endif
 #include "LinkManager.h"
 
@@ -758,7 +758,7 @@ static void initialize_logics(Config &cfg)
     {
       logic = new ReflectorLogic(cfg, logic_name);
     }
-#ifdef PJSIP_MAJOR
+#ifdef WITH_CONTRIB_SIP_LOGIC
     else if (logic_type == "Sip")
     {
       logic = new SipLogic(cfg, logic_name);