diff --git a/2015/yang/Makefile b/2015/yang/Makefile
index 4f5d37bbe..e35e6b12e 100644
--- a/2015/yang/Makefile
+++ b/2015/yang/Makefile
@@ -74,7 +74,7 @@ CFLAGS= ${CSTD} ${CWARN} ${ARCH} ${CDEFINE} ${CINCLUDE} ${OPT}
 
 # Libraries needed to build
 #
-LIBS=
+LIBS= -lm
 
 # C compiler to use
 #
diff --git a/thanks-for-fixes.md b/thanks-for-fixes.md
index b5f376d17..281ef0d93 100644
--- a/thanks-for-fixes.md
+++ b/thanks-for-fixes.md
@@ -1311,6 +1311,8 @@ time.
 Cody fixed an unfortunate typo in the Makefile that was preventing some of the
 files from compiling properly, trying instead to compile already compiled code.
 
+He also added explicit linking of libm (`-lm`) for systems that do not do this
+(linux seems to not but macOS does).
 
 
 ## [2019/ciura](2019/ciura/prog.c) ([README.md](2019/ciura/README.md]))