diff --git config/system-headers config/system-headers
index 8803150..ae38d68 100644
--- config/system-headers
+++ config/system-headers
@@ -1158,3 +1158,4 @@ unicode/unum.h
 unicode/ustring.h
 #endif
 libutil.h
+unwind.h
diff --git configure.in configure.in
index f452a5e..a1ebbcc 100644
--- configure.in
+++ configure.in
@@ -7455,7 +7455,10 @@ dnl ========================================================
 dnl = Support for gcc stack unwinding (from gcc 3.3)
 dnl ========================================================
 if test -z "$SKIP_LIBRARY_CHECKS"; then
+    AC_LANG_SAVE
+    AC_LANG_CPLUSPLUS
     MOZ_CHECK_HEADER(unwind.h, AC_CHECK_FUNCS(_Unwind_Backtrace))
+    AC_LANG_RESTORE
 fi
 
 dnl ========================================================
diff --git config/system-headers config/system-headers
index 8803150..ae38d68 100644
--- js/src/config/system-headers
+++ js/src/config/system-headers
@@ -1158,3 +1158,4 @@ unicode/unum.h
 unicode/ustring.h
 #endif
 libutil.h
+unwind.h
diff --git configure.in configure.in
index f452a5e..a1ebbcc 100644
--- js/src/configure.in
+++ js/src/configure.in
@@ -7455,7 +7455,10 @@ dnl ========================================================
 dnl = Support for gcc stack unwinding (from gcc 3.3)
 dnl ========================================================
 if test -z "$SKIP_LIBRARY_CHECKS"; then
+    AC_LANG_SAVE
+    AC_LANG_CPLUSPLUS
     MOZ_CHECK_HEADER(unwind.h, AC_CHECK_FUNCS(_Unwind_Backtrace))
+    AC_LANG_RESTORE
 fi
 
 dnl ========================================================