diff --git a/calc-c99.patch b/calc-c99.patch
new file mode 100644
index 0000000..772bcff
--- /dev/null
+++ b/calc-c99.patch
@@ -0,0 +1,46 @@
+Include <string.h> for the memset function, to avoid an implicit
+function declaration.
+
+Submitted upstream: <https://github.com/lcn2/calc/pull/68>
+
+diff --git a/Makefile b/Makefile
+index 99bce2a9d1f77199..9f1b8dc8a2779456 100644
+--- a/Makefile
++++ b/Makefile
+@@ -3218,7 +3218,7 @@ have_fgetsetpos.h: have_fgetsetpos.c banned.h have_ban_pragma.h ${MAKE_FILE} ${L
+ 	    ${TRUE}; \
+ 	fi
+ 
+-have_fpos_pos.h: have_fpos_pos.c have_fgetsetpos.h have_posscl.h \
++have_fpos_pos.h: have_fpos_pos.c have_fgetsetpos.h have_posscl.h have_string.h \
+ 		 banned.h have_ban_pragma.h ${MAKE_FILE} ${LOC_MKF}
+ 	${Q} ${RM} -f fpos_tmp $@
+ 	${H} echo 'forming $@'
+diff --git a/Makefile.simple b/Makefile.simple
+index fd97064b045dc9dc..3d82f06dc1ddf67e 100644
+--- a/Makefile.simple
++++ b/Makefile.simple
+@@ -2532,7 +2532,7 @@ have_fgetsetpos.h: have_fgetsetpos.c banned.h have_ban_pragma.h ${MAKE_FILE} ${L
+ 	    ${TRUE}; \
+ 	fi
+ 
+-have_fpos_pos.h: have_fpos_pos.c have_fgetsetpos.h have_posscl.h \
++have_fpos_pos.h: have_fpos_pos.c have_fgetsetpos.h have_posscl.h have_string.h \
+ 		 banned.h have_ban_pragma.h ${MAKE_FILE} ${LOC_MKF}
+ 	${Q} ${RM} -f fpos_tmp $@
+ 	${H} echo 'forming $@'
+diff --git a/have_fpos_pos.c b/have_fpos_pos.c
+index 72e2fa43ed423df7..0527905247b1b1e7 100644
+--- a/have_fpos_pos.c
++++ b/have_fpos_pos.c
+@@ -28,6 +28,10 @@
+ #include <stdio.h>
+ #include "have_fgetsetpos.h"
+ #include "have_posscl.h"
++#include "have_string.h"
++#ifdef HAVE_STRING_H
++# include <string.h>
++#endif
+ 
+ 
+ #include "banned.h"	/* include after system header <> includes */
diff --git a/calc.spec b/calc.spec
index a876b5b..872978b 100644
--- a/calc.spec
+++ b/calc.spec
@@ -24,6 +24,7 @@ URL:           http://isthe.com/chongo/tech/comp/calc/
 Source0:       https://github.com/lcn2/calc/releases/download/v%{version}/calc-%{version}.tar.bz2
 Source1:       calc-converted-to-gpl.txt
 Source2:       calc-COPYING-GPL
+Patch0: calc-c99.patch
 
 BuildRequires: gcc, sed, util-linux
 
@@ -81,7 +82,7 @@ useful in themselves.
 
 
 %prep
-%setup -q
+%autosetup -p1
 
 %if %{with_readline}
   for f in help.c version.c calc.man $( ls help/*|grep  '^help/credit$' ) ; do