diff --git a/config/config.mk b/config/config.mk
index 537e67040bc3..f405445ebfd9 100644
--- a/config/config.mk
+++ b/config/config.mk
@@ -880,6 +880,10 @@ EXPAND_MOZLIBNAME = $(foreach lib,$(1),$(DIST)/lib/$(LIB_PREFIX)$(lib).$(LIB_SUF
 PLY_INCLUDE = -I$(topsrcdir)/other-licenses/ply
 
 export CL_INCLUDES_PREFIX
+# Make sure that the build system can handle non-ASCII characters
+# in environment variables to prevent it from breking silently on
+# non-English systems.
+export NONASCII
 
 ifdef MOZ_GTK2_CFLAGS
 MOZ_GTK2_CFLAGS := -I$(topsrcdir)/widget/gtk/compat $(MOZ_GTK2_CFLAGS)
diff --git a/configure.in b/configure.in
index 308ece3e34cd..2e6474738503 100644
--- a/configure.in
+++ b/configure.in
@@ -7705,6 +7705,12 @@ else
   fi
 fi
 
+dnl Make sure that the build system can handle non-ASCII characters
+dnl in environment variables to prevent it from breking silently on
+dnl non-English systems.
+NONASCII=$'\241\241'
+AC_SUBST(NONASCII)
+
 dnl ========================================================
 dnl =
 dnl = Static Build Options
diff --git a/js/src/config/config.mk b/js/src/config/config.mk
index 537e67040bc3..f405445ebfd9 100644
--- a/js/src/config/config.mk
+++ b/js/src/config/config.mk
@@ -880,6 +880,10 @@ EXPAND_MOZLIBNAME = $(foreach lib,$(1),$(DIST)/lib/$(LIB_PREFIX)$(lib).$(LIB_SUF
 PLY_INCLUDE = -I$(topsrcdir)/other-licenses/ply
 
 export CL_INCLUDES_PREFIX
+# Make sure that the build system can handle non-ASCII characters
+# in environment variables to prevent it from breking silently on
+# non-English systems.
+export NONASCII
 
 ifdef MOZ_GTK2_CFLAGS
 MOZ_GTK2_CFLAGS := -I$(topsrcdir)/widget/gtk/compat $(MOZ_GTK2_CFLAGS)
diff --git a/js/src/configure.in b/js/src/configure.in
index c71a23398652..8903411bbd3e 100644
--- a/js/src/configure.in
+++ b/js/src/configure.in
@@ -3820,6 +3820,12 @@ else
   fi
 fi
 
+dnl Make sure that the build system can handle non-ASCII characters
+dnl in environment variables to prevent it from breking silently on
+dnl non-English systems.
+NONASCII=$'\241\241'
+AC_SUBST(NONASCII)
+
 dnl ========================================================
 dnl = Disable -fstrict-aliasing with GCC 4.4 and earlier.
 dnl = See bugs 821502 and 832623.