diff --git a/Makefile.in b/Makefile.in
index ad7cf7a6b56..655dfa0e0b3 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -14,7 +14,11 @@ CFG_INFO := $(info cfg: building on $(CFG_OSTYPE) $(CFG_CPUTYPE))
 CFG_GCC_CFLAGS := -fno-strict-aliasing
 CFG_GCC_LINK_FLAGS :=
 CFG_BOOT_FLAGS := $(BOOT_FLAGS)
-CFG_RUSTC_FLAGS := -nowarn -O
+ifdef CFG_DISABLE_OPTIMIZE
+  CFG_RUSTC_FLAGS := -O
+else
+  CFG_RUSTC_FLAGS := -nowarn -O
+endif
 
 # On Darwin, we need to run dsymutil so the debugging information ends
 # up in the right place.  On other platforms, it automatically gets
diff --git a/configure b/configure
index 8c8ed680a1b..2f3a9d43f43 100755
--- a/configure
+++ b/configure
@@ -153,6 +153,7 @@ fi
 
 opt valgrind 1 "run tests with valgrind"
 opt docs     1 "build documentation"
+opt optimize 1 "build optimized rust code"
 
 
 if [ $HELP -eq 1 ]