diff --git a/bin/xbps-bin/main.c b/bin/xbps-bin/main.c
index 51e82088502..e4d8d9ec707 100644
--- a/bin/xbps-bin/main.c
+++ b/bin/xbps-bin/main.c
@@ -27,6 +27,7 @@
 #include <stdbool.h>
 #include <stdlib.h>
 #include <string.h>
+#include <strings.h>
 #include <errno.h>
 #include <limits.h>
 #include <libgen.h>
diff --git a/bin/xbps-pkgdb/main.c b/bin/xbps-pkgdb/main.c
index 8d093174577..f70aad905ee 100644
--- a/bin/xbps-pkgdb/main.c
+++ b/bin/xbps-pkgdb/main.c
@@ -27,6 +27,7 @@
 #include <stdbool.h>
 #include <stdlib.h>
 #include <string.h>
+#include <strings.h>
 #include <errno.h>
 #include <limits.h>
 
diff --git a/bin/xbps-repo/main.c b/bin/xbps-repo/main.c
index 036191a7194..0fa1a3a13c0 100644
--- a/bin/xbps-repo/main.c
+++ b/bin/xbps-repo/main.c
@@ -27,6 +27,7 @@
 #include <stdbool.h>
 #include <stdlib.h>
 #include <string.h>
+#include <strings.h>
 #include <errno.h>
 #include <limits.h>
 #include <libgen.h>
diff --git a/lib/cmpver.c b/lib/cmpver.c
index 4bc828811a2..d946f17e251 100644
--- a/lib/cmpver.c
+++ b/lib/cmpver.c
@@ -19,6 +19,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <strings.h>
 #include <ctype.h>
 #include <xbps_api.h>
 
diff --git a/lib/fexec.c b/lib/fexec.c
index 4f10078e88c..0319c0549fa 100644
--- a/lib/fexec.c
+++ b/lib/fexec.c
@@ -35,6 +35,8 @@
 #include <unistd.h>
 #include <string.h>
 
+#include <xbps_api.h>
+
 static int	vfcexec(const char *, int, const char *, va_list);
 static int	pfcexec(const char *, const char *, const char **);
 
diff --git a/vars.mk b/vars.mk
index ecb45731afa..b9c3c602c01 100644
--- a/vars.mk
+++ b/vars.mk
@@ -8,5 +8,7 @@ TOPDIR	?= ..
 INSTALL_STRIPPED ?= -s
 
 LDFLAGS += -L$(TOPDIR)/lib -L$(PREFIX)/lib -lxbps
-CPPFLAGS += -I$(TOPDIR)/include
-CFLAGS += -O2 -Wall -Wextra -Werror -fPIC -DPIC
+CPPFLAGS += -I$(TOPDIR)/include -D_XOPEN_SOURCE=600
+WARNFLAGS ?= -pedantic -std=c99 -Wall -Wextra -Werror -Wshadow -Wformat=2
+WARNFLAGS += -Wmissing-declarations -Wcomment -Wunused-macros -Wendif-labels
+CFLAGS += $(WARNFLAGS) -O2 -fPIC -DPIC