diff --git a/Makefile.am b/Makefile.am
index 2c91d7cb..5fa37703 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -20,3 +20,4 @@ i3blocks_SOURCES = \
 	sys.c \
 	sys.h \
 	term.h
+i3blocks_CFLAGS = -Wall -Wextra -Werror $(AM_CFLAGS)
diff --git a/block.c b/block.c
index af71b244..a7e999d9 100644
--- a/block.c
+++ b/block.c
@@ -60,6 +60,8 @@ static int block_setenv(const char *name, const char *value, void *data)
 {
 	int err;
 
+	(void)data;
+
 	if (!value)
 		value = "";
 
@@ -182,7 +184,6 @@ static int block_send_json(struct block *block)
 static int block_send(struct block *block)
 {
 	const char *button = block_get(block, "button");
-	int err;
 
 	if (!button) {
 		block_error(block, "no click data to send");
@@ -217,6 +218,8 @@ void block_touch(struct block *block)
 	unsigned long now;
 	int err;
 
+	(void)block;
+
 	err = sys_gettime(&now);
 	if (err) {
 		block_error(block, "failed to touch block");
@@ -236,6 +239,8 @@ static int block_child_sig(struct block *block)
 	sigset_t set;
 	int err;
 
+	(void)block;
+
 	/* It'd be safe to assume that all signals are unblocked by default */
 	err = sys_sigfillset(&set);
 	if (err)
@@ -482,7 +487,6 @@ int block_reap(struct block *block)
 static int i3blocks_setup(struct block *block)
 {
 	const char *value;
-	int err;
 
 	value = map_get(block->config, "command");
 	if (value && *value != '\0')
@@ -584,7 +588,7 @@ void block_printf(struct block *block, int lvl, const char *fmt, ...)
 	va_list ap;
 	int err;
 
-	if (lvl > log_level)
+	if (lvl > (int)log_level)
 		return;
 
 	va_start(ap, fmt);
diff --git a/block.h b/block.h
index a43816cc..abed98d4 100644
--- a/block.h
+++ b/block.h
@@ -50,7 +50,7 @@ struct block {
 	/* Shortcuts */
 	const char *command;
 	int interval;
-	unsigned signal;
+	int signal;
 	unsigned format;
 
 	/* Runtime info */
diff --git a/configure.ac b/configure.ac
index 1856185d..c3cc6218 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1,6 +1,6 @@
 AC_INIT([i3blocks], 1.4)
 AC_CONFIG_AUX_DIR([build-aux])
-AM_INIT_AUTOMAKE(foreign)
+AM_INIT_AUTOMAKE([-Wall -Werror foreign])
 AC_PROG_CC
 AC_CONFIG_HEADERS([i3blocks-config.h])
 AC_CONFIG_FILES([
diff --git a/ini.c b/ini.c
index 4a494ff4..7e984541 100644
--- a/ini.c
+++ b/ini.c
@@ -47,6 +47,8 @@ static int ini_property(struct ini *ini, char *key, char *value)
 
 static int ini_parse_line(char *line, size_t num, void *data)
 {
+	(void)num;
+
 	/* comment or empty line? */
 	if (*line == '\0' || *line == '#')
 		return 0;
diff --git a/json.c b/json.c
index 8f84130d..65b4ca88 100644
--- a/json.c
+++ b/json.c
@@ -347,6 +347,8 @@ static int json_line_cb(char *line, size_t num, void *data)
 	size_t len;
 	int err;
 
+	(void)num;
+
 	for (;;) {
 		/* Only support inline flattened structures at the moment */
 		while (*line == '[' || *line == ']' || *line == ',' ||
@@ -452,7 +454,7 @@ int json_escape(const char *str, char *buf, size_t size)
 		}
 
 		/* Ensure the result was not truncated */
-		if (len < 0 || len >= size)
+		if (len < 0 || (size_t)len >= size)
 			return -ENOSPC;
 
 		size -= len;
diff --git a/log.h b/log.h
index a1ef2858..42ce7221 100644
--- a/log.h
+++ b/log.h
@@ -40,7 +40,7 @@ static inline void log_printf(int lvl, const char *fmt, ...)
 {
 	va_list ap;
 
-	if (lvl <= LOG_ERROR || lvl <= log_level) {
+	if (lvl <= LOG_ERROR || lvl <= (int)log_level) {
 		va_start(ap, fmt);
 		vfprintf(stderr, fmt, ap);
 		va_end(ap);