diff --git a/Makefile b/Makefile
index f31293e90..45493a8dc 100644
--- a/Makefile
+++ b/Makefile
@@ -39,7 +39,7 @@ export REDIS_TEST_CONFIG
 CC:=$(shell sh -c 'type $${CC%% *} >/dev/null 2>/dev/null && echo $(CC) || echo gcc')
 CXX:=$(shell sh -c 'type $${CXX%% *} >/dev/null 2>/dev/null && echo $(CXX) || echo g++')
 OPTIMIZATION?=-O3
-WARNINGS=-Wall -W -Wstrict-prototypes -Wwrite-strings -Wno-missing-field-initializers
+WARNINGS=-Wall -Wextra -Werror -Wstrict-prototypes -Wwrite-strings -Wno-missing-field-initializers
 DEBUG_FLAGS?= -g -ggdb
 REAL_CFLAGS=$(OPTIMIZATION) -fPIC $(CPPFLAGS) $(CFLAGS) $(WARNINGS) $(DEBUG_FLAGS) $(PLATFORM_FLAGS)
 REAL_LDFLAGS=$(LDFLAGS)
diff --git a/hiredis.c b/hiredis.c
index 9d8a500c7..446ceb1e6 100644
--- a/hiredis.c
+++ b/hiredis.c
@@ -392,12 +392,12 @@ int redisvFormatCommand(char **target, const char *format, va_list ap) {
                     while (*_p != '\0' && strchr(flags,*_p) != NULL) _p++;
 
                     /* Field width */
-                    while (*_p != '\0' && isdigit(*_p)) _p++;
+                    while (*_p != '\0' && isdigit((int) *_p)) _p++;
 
                     /* Precision */
                     if (*_p == '.') {
                         _p++;
-                        while (*_p != '\0' && isdigit(*_p)) _p++;
+                        while (*_p != '\0' && isdigit((int) *_p)) _p++;
                     }
 
                     /* Copy va_list before consuming with va_arg */
diff --git a/sds.c b/sds.c
index a20ba1912..21ecec04e 100644
--- a/sds.c
+++ b/sds.c
@@ -886,7 +886,7 @@ sds sdscatrepr(sds s, const char *p, size_t len) {
         case '\a': s = sdscatlen(s,"\\a",2); break;
         case '\b': s = sdscatlen(s,"\\b",2); break;
         default:
-            if (isprint(*p))
+            if (isprint((int) *p))
                 s = sdscatprintf(s,"%c",*p);
             else
                 s = sdscatprintf(s,"\\x%02x",(unsigned char)*p);
@@ -948,7 +948,7 @@ sds *sdssplitargs(const char *line, int *argc) {
     *argc = 0;
     while(1) {
         /* skip blanks */
-        while(*p && isspace(*p)) p++;
+        while(*p && isspace((int) *p)) p++;
         if (*p) {
             /* get a token */
             int inq=0;  /* set to 1 if we are in "quotes" */
@@ -959,8 +959,8 @@ sds *sdssplitargs(const char *line, int *argc) {
             while(!done) {
                 if (inq) {
                     if (*p == '\\' && *(p+1) == 'x' &&
-                                             isxdigit(*(p+2)) &&
-                                             isxdigit(*(p+3)))
+                                             isxdigit((int) *(p+2)) &&
+                                             isxdigit((int) *(p+3)))
                     {
                         unsigned char byte;
 
@@ -984,7 +984,7 @@ sds *sdssplitargs(const char *line, int *argc) {
                     } else if (*p == '"') {
                         /* closing quote must be followed by a space or
                          * nothing at all. */
-                        if (*(p+1) && !isspace(*(p+1))) goto err;
+                        if (*(p+1) && !isspace((int) *(p+1))) goto err;
                         done=1;
                     } else if (!*p) {
                         /* unterminated quotes */
@@ -999,7 +999,7 @@ sds *sdssplitargs(const char *line, int *argc) {
                     } else if (*p == '\'') {
                         /* closing quote must be followed by a space or
                          * nothing at all. */
-                        if (*(p+1) && !isspace(*(p+1))) goto err;
+                        if (*(p+1) && !isspace((int) *(p+1))) goto err;
                         done=1;
                     } else if (!*p) {
                         /* unterminated quotes */
diff --git a/test.c b/test.c
index f3cb73434..a9afe904c 100644
--- a/test.c
+++ b/test.c
@@ -1567,6 +1567,9 @@ static void test_throughput(struct config config) {
 // }
 
 #ifdef HIREDIS_TEST_ASYNC
+
+#pragma GCC diagnostic ignored "-Woverlength-strings"   /* required on gcc 4.8.x due to assert statements */
+
 struct event_base *base;
 
 typedef struct TestState {