diff --git a/Installation/include/CGAL/config.h b/Installation/include/CGAL/config.h
index daab1608122..2b392b6d8ca 100644
--- a/Installation/include/CGAL/config.h
+++ b/Installation/include/CGAL/config.h
@@ -369,17 +369,17 @@ using std::max;
 #  define CGAL_NO_UNIQUE_ADDRESS
 #endif
 
-// Macro CGAL_ASSUME and CGAL_unreachable
+// Macro CGAL_ASSUME and CGAL_UNREACHABLE
 // Call a builtin of the compiler to pass a hint to the compiler
 #if __has_builtin(__builtin_unreachable) || (CGAL_GCC_VERSION > 0 && !__STRICT_ANSI__)
 // From g++ 4.5, there exists a __builtin_unreachable()
 // Also in LLVM/clang
 #  define CGAL_ASSUME(EX) if(!(EX)) { __builtin_unreachable(); }
-#  define CGAL_unreachable() __builtin_unreachable()
+#  define CGAL_UNREACHABLE() __builtin_unreachable()
 #elif defined(_MSC_VER)
 // MSVC has __assume
 #  define CGAL_ASSUME(EX) __assume(EX)
-#  define CGAL_unreachable() __assume(0)
+#  define CGAL_UNREACHABLE() __assume(0)
 #endif
 // If CGAL_ASSUME is not defined, then CGAL_assume and CGAL_assume_code are
 // defined differently, in <CGAL/assertions.h>
diff --git a/STL_Extension/include/CGAL/assertions.h b/STL_Extension/include/CGAL/assertions.h
index 293a2abe557..e7357ecd8d1 100644
--- a/STL_Extension/include/CGAL/assertions.h
+++ b/STL_Extension/include/CGAL/assertions.h
@@ -79,14 +79,6 @@ inline bool possibly(Uncertain<bool> c);
 #  define CGAL_destructor_assertion_catch(CODE) CODE
 #  define CGAL_assertion_msg(EX,MSG) (static_cast<void>(0))
 #  define CGAL_assertion_code(CODE)
-#  ifdef CGAL_ASSUME
-#    define CGAL_assume(EX) CGAL_ASSUME(EX)
-#    define CGAL_assume_code(CODE) CODE
-#  else // not def CGAL_ASSUME
-#    define CGAL_assume(EX)  CGAL_assertion(EX)
-#    define CGAL_unreachable()  CGAL_assertion(false)
-#    define CGAL_assume_code(CODE) CGAL_assertion_code(CODE)
-#  endif // not def CGAL_ASSUME
 #else // no CGAL_NO_ASSERTIONS
 #  define CGAL_ASSERTIONS_ENABLED true
 #  define CGAL_assertion(EX) \
@@ -103,10 +95,22 @@ inline bool possibly(Uncertain<bool> c);
 #  define CGAL_assertion_msg(EX,MSG)                                    \
    (CGAL::possibly(EX)?(static_cast<void>(0)): ::CGAL::assertion_fail( # EX , __FILE__, __LINE__, MSG))
 #  define CGAL_assertion_code(CODE) CODE
-#  define CGAL_assume(EX) CGAL_assertion(EX)
-#  define CGAL_assume_code(CODE) CGAL_assertion_code(CODE)
 #endif // no CGAL_NO_ASSERTIONS
 
+#  ifdef CGAL_ASSUME
+#    define CGAL_assume(EX) CGAL_ASSUME(EX)
+#    define CGAL_assume_code(CODE) CODE
+#  else // not def CGAL_ASSUME
+#    define CGAL_assume(EX)  CGAL_assertion(EX)
+#    define CGAL_assume_code(CODE) CGAL_assertion_code(CODE)
+#  endif // CGAL_ASSUME
+
+#  ifdef CGAL_UNREACHABLE
+#    define CGAL_unreachable() CGAL_UNREACHABLE()
+#  else // not def CGAL_UNREACHABLE
+#    define CGAL_unreachable()  CGAL_assertion(false)
+#  endif // CGAL_UNREACHABLE
+
 # define CGAL_static_assertion(EX) \
      static_assert(EX, #EX)