diff --git a/external_libs/mvtnorm/Makefile b/external_libs/mvtnorm/Makefile
index ac3d3893..29f883db 100644
--- a/external_libs/mvtnorm/Makefile
+++ b/external_libs/mvtnorm/Makefile
@@ -5,8 +5,11 @@ CC   ?= gcc
 FC   ?= gfortran
 
 UNAME_S := $(shell uname -s)
+UNAME_M := $(shell uname -m)
 ifeq ($(UNAME_S),Darwin)
- FLAG += -arch x86_64
+ ifeq ($(UNAME_M),x86_64)
+  FLAG += -arch x86_64
+ endif
 endif
 
 libMvtnorm.a: mvtnorm.o mvt.o randomF77.o
diff --git a/external_libs/pgenlib/Makefile b/external_libs/pgenlib/Makefile
index 262d920b..5ed281d8 100644
--- a/external_libs/pgenlib/Makefile
+++ b/external_libs/pgenlib/Makefile
@@ -7,8 +7,11 @@ CXXFLAGS    = -O3 -Wall -std=c++11
 CFLAGS      = 
 
 UNAME_S := $(shell uname -s)
+UNAME_M := $(shell uname -m)
 ifeq ($(UNAME_S),Darwin)
- CXXFLAGS += -arch x86_64
+ ifeq ($(UNAME_M),x86_64)
+  CXXFLAGS += -arch x86_64
+ endif
 endif
 
 OBJECTS       = $(patsubst %.cc,%.o,$(wildcard ./include/*.cc)) $(patsubst %.cpp,%.o,$(wildcard *.cpp))  $(patsubst %.cc,%.o,$(wildcard *.cc))
diff --git a/external_libs/qf/Makefile b/external_libs/qf/Makefile
index 3d0341ac..f139e65f 100644
--- a/external_libs/qf/Makefile
+++ b/external_libs/qf/Makefile
@@ -3,8 +3,11 @@ CXX      ?= g++
 CXXFLAGS  = -O2 -DNDEBUG -fPIC
 
 UNAME_S := $(shell uname -s)
+UNAME_M := $(shell uname -m)
 ifeq ($(UNAME_S),Darwin)
- CXXFLAGS += -arch x86_64
+ ifeq ($(UNAME_M),x86_64)
+  CXXFLAGS += -arch x86_64
+ endif
 endif
 
 qf.a: qfc.o
diff --git a/external_libs/quadpack/Makefile b/external_libs/quadpack/Makefile
index e160de35..f70f0b1f 100644
--- a/external_libs/quadpack/Makefile
+++ b/external_libs/quadpack/Makefile
@@ -3,8 +3,11 @@ AR   ?= ar
 FC   ?= gfortran
 
 UNAME_S := $(shell uname -s)
+UNAME_M := $(shell uname -m)
 ifeq ($(UNAME_S),Darwin)
- FLAG += -arch x86_64
+ ifeq ($(UNAME_M),x86_64)
+  FLAG += -arch x86_64
+ endif
 endif
 
 OBJECTS = $(patsubst %.f,%.o,$(wildcard ./*.f))
diff --git a/external_libs/remeta/Makefile b/external_libs/remeta/Makefile
index 543c5c7e..9d5f2aad 100644
--- a/external_libs/remeta/Makefile
+++ b/external_libs/remeta/Makefile
@@ -12,8 +12,11 @@ ifneq ($(strip $(HTSLIB_PATH)),) # defined externally
 endif
 
 UNAME_S := $(shell uname -s)
+UNAME_M := $(shell uname -m)
 ifeq ($(UNAME_S),Darwin)
-	CXXFLAGS += -arch x86_64
+ ifeq ($(UNAME_M),x86_64)
+	 CXXFLAGS += -arch x86_64
+ endif
 endif
 
 OBJECTS       = bgz_writer.o regenie_ld_matrix_writer.o