--- src/Makefile
+++ src/Makefile
@@ -83,7 +83,7 @@
 
 SRCS1=$(speak_SOURCES)
 OBJS1=$(patsubst %.cpp,%.o,$(SRCS1))
-LIBS1=         $(LIB_AUDIO)           $(EXTRA_LIBS)
+LIBS1=         $(LIB_AUDIO)           -lm $(EXTRA_LIBS)
 
 SRCS2=$(libespeak_SOURCES)
 OBJS2=$(patsubst %.cpp,x_%.o,$(SRCS2))
@@ -91,7 +91,7 @@
 
 SRCS3 = espeak.cpp
 OBJS3=$(patsubst %.cpp,%.o,$(SRCS3))
-LIBS3=         -L . -lespeak
+LIBS3=         -L . -lespeak -lm
 
 CXXFLAGS=-O2