diff --git a/ports/unix/Makefile b/ports/unix/Makefile
index b840856ffa..bcc76ce160 100644
--- a/ports/unix/Makefile
+++ b/ports/unix/Makefile
@@ -188,6 +188,9 @@ CFLAGS += -DMPZ_DIG_SIZE=16 # force 16 bits to work on both 32 and 64 bit archs
 MPY_CROSS_FLAGS += -mcache-lookup-bc
 endif
 
+ifneq ($(FROZEN_MANIFEST)$(FROZEN_DIR),)
+CFLAGS += -DMICROPY_MODULE_FROZEN_STR
+endif
 
 include $(TOP)/py/mkrules.mk
 
@@ -212,7 +215,7 @@ uninstall:
 
 # build synthetically fast interpreter for benchmarking
 fast:
-	$(MAKE) COPT="-O2 -DNDEBUG -fno-crossjumping" CFLAGS_EXTRA='-DMP_CONFIGFILE="<mpconfigport_fast.h>"' BUILD=build-fast PROG=micropython_fast
+	$(MAKE) COPT="-O2 -DNDEBUG -fno-crossjumping" CFLAGS_EXTRA='-DMP_CONFIGFILE="<mpconfigport_fast.h>"' BUILD=build-fast PROG=micropython_fast FROZEN_MANIFEST=
 
 # build a minimal interpreter
 minimal:
diff --git a/ports/unix/mpconfigport.h b/ports/unix/mpconfigport.h
index 0ff6b2b06d..1bb80f9704 100644
--- a/ports/unix/mpconfigport.h
+++ b/ports/unix/mpconfigport.h
@@ -113,7 +113,6 @@
 #define MICROPY_PY_IO_IOBASE        (1)
 #define MICROPY_PY_IO_FILEIO        (1)
 #define MICROPY_PY_GC_COLLECT_RETVAL (1)
-#define MICROPY_MODULE_FROZEN_STR   (1)
 
 #ifndef MICROPY_STACKLESS
 #define MICROPY_STACKLESS           (0)
diff --git a/ports/unix/mpconfigport_fast.h b/ports/unix/mpconfigport_fast.h
index 442159eb4f..193567a294 100644
--- a/ports/unix/mpconfigport_fast.h
+++ b/ports/unix/mpconfigport_fast.h
@@ -33,8 +33,3 @@
 // 91 is a magic number proposed by @dpgeorge, which make pystone run ~ at tie
 // with CPython 3.4.
 #define MICROPY_MODULE_DICT_SIZE (91)
-
-// Don't include builtin upip, as this build is again intended just for
-// synthetic benchmarking
-#undef MICROPY_MODULE_FROZEN_STR
-#define MICROPY_MODULE_FROZEN_STR (0)