diff --git a/CMakeLists.txt b/CMakeLists.txt
index f5c1e5535..5bf3e4910 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -234,13 +234,12 @@ set (_PC_FIELDS
 
 set (_PC_HEADERS ucontext.h signal.h)
 
-if (HAVE_UCONTEXT_H AND NOT PC_FROM_UCONTEXT)
+if (HAVE_UCONTEXT_H AND NOT DEFINED PC_FROM_UCONTEXT)
   foreach (_PC_FIELD ${_PC_FIELDS})
     foreach (_PC_HEADER ${_PC_HEADERS})
       set (_TMP
       ${CMAKE_CURRENT_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeTmp/uctfield.cpp)
       file (WRITE ${_TMP} "
-#define _GNU_SOURCE 1
 #include <${_PC_HEADER}>
 int main(void)
 {
@@ -249,14 +248,15 @@ int main(void)
 }
 ")
       try_compile (HAVE_PC_FROM_UCONTEXT ${CMAKE_CURRENT_BINARY_DIR} ${_TMP}
-        COMPILE_DEFINITIONS _GNU_SOURCE=1)
+        COMPILE_DEFINITIONS -D_GNU_SOURCE)
 
       if (HAVE_PC_FROM_UCONTEXT)
-        set (PC_FROM_UCONTEXT ${_PC_FIELD} CACHE)
+        set (PC_FROM_UCONTEXT ${_PC_FIELD} CACHE STRING "")
+        break ()
       endif (HAVE_PC_FROM_UCONTEXT)
     endforeach (_PC_HEADER)
   endforeach (_PC_FIELD)
-endif  (HAVE_UCONTEXT_H AND NOT PC_FROM_UCONTEXT)
+endif (HAVE_UCONTEXT_H AND NOT DEFINED PC_FROM_UCONTEXT)
 
 set (GOOGLE_NAMESPACE google)
 set (_START_GOOGLE_NAMESPACE_ "namespace ${GOOGLE_NAMESPACE} {")
diff --git a/src/config.h.cmake.in b/src/config.h.cmake.in
index 9d6101013..5a4b0d092 100644
--- a/src/config.h.cmake.in
+++ b/src/config.h.cmake.in
@@ -135,7 +135,7 @@
 #cmakedefine LT_OBJDIR
 
 /* How to access the PC from a struct ucontext */
-#cmakedefine PC_FROM_UCONTEXT
+#cmakedefine PC_FROM_UCONTEXT ${PC_FROM_UCONTEXT}
 
 /* define if we should print file offsets in traces instead of symbolizing. */
 #cmakedefine PRINT_UNSYMBOLIZED_STACK_TRACES