diff --git a/Makefile.in b/Makefile.in
index 5c1c860..f5bcf4e 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -33,7 +33,7 @@ CSFLAGS		=	-s "$(CODESIGN_IDENTITY)" @CSFLAGS@ --timestamp
 DSOFLAGS	=	@DSOFLAGS@ $(CFLAGS)
 INSTALL		=	@INSTALL@
 LDFLAGS		=	@LDFLAGS@ $(OPTIM)
-LIBS		=	@LIBS@
+LIBS		=	@LIBS@ -lm
 LN		=	@LN@
 OPTIM		=	@OPTIM@
 RANLIB		=	@RANLIB@
diff --git a/pdfio.pc.in b/pdfio.pc.in
index b869e79..e86456b 100644
--- a/pdfio.pc.in
+++ b/pdfio.pc.in
@@ -9,5 +9,5 @@ Version: @PDFIO_VERSION@
 URL: https://www.msweet.org/pdfio
 Requires: @PKGCONFIG_REQUIRES@
 Libs: @PKGCONFIG_LIBS@
-Libs.private: @PKGCONFIG_LIBS_PRIVATE@
+Libs.private: @PKGCONFIG_LIBS_PRIVATE@ -lm
 Cflags: @PKGCONFIG_CFLAGS@