diff --git a/GNUmakefile b/GNUmakefile
index 9e540d92..2cf7d8fd 100755
--- a/GNUmakefile
+++ b/GNUmakefile
@@ -2,8 +2,9 @@
 #####        System Attributes and Programs           #####
 ###########################################################
 
-# Must use Bash
-SHELL = bash
+# https://www.gnu.org/software/make/manual/make.html#Makefile-Conventions
+SHELL = /bin/sh
+
 # If needed
 TMPDIR ?= /tmp
 # Used for ARMv7 and NEON.
diff --git a/GNUmakefile-cross b/GNUmakefile-cross
index 379005c4..7ab6ccfe 100755
--- a/GNUmakefile-cross
+++ b/GNUmakefile-cross
@@ -1,3 +1,6 @@
+# https://www.gnu.org/software/make/manual/make.html#Makefile-Conventions
+SHELL = /bin/sh
+
 # Default CXXFLAGS if none were provided
 CXXFLAGS ?= -DNDEBUG -g2 -O3 -fPIC -pipe