diff --git a/src/Makefile b/src/Makefile
index e9e93a96a..a6e4b2098 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -34,8 +34,10 @@ endif
 WARN=-Wall -W -Wno-missing-field-initializers
 OPT=$(OPTIMIZATION)
 
-# Detect if the compiler supports C11 _Atomic
-C11_ATOMIC := $(shell sh -c 'echo "\#include <stdatomic.h>" > foo.c; \
+# Detect if the compiler supports C11 _Atomic.
+# NUMBER_SIGN_CHAR is a workaround to support both GNU Make 4.3 and older versions.
+NUMBER_SIGN_CHAR := \#
+C11_ATOMIC := $(shell sh -c 'echo "$(NUMBER_SIGN_CHAR)include <stdatomic.h>" > foo.c; \
 	$(CC) -std=c11 -c foo.c -o foo.o > /dev/null 2>&1; \
 	if [ -f foo.o ]; then echo "yes"; rm foo.o; fi; rm foo.c')
 ifeq ($(C11_ATOMIC),yes)