diff --git a/mongoose.c b/mongoose.c
index d856b4e8..9f6d5631 100644
--- a/mongoose.c
+++ b/mongoose.c
@@ -1090,11 +1090,11 @@ void mg_http_serve_dir(struct mg_connection *c, struct mg_http_message *hm,
   char t1[MG_PATH_MAX], t2[sizeof(t1)];
   t1[0] = t2[0] = '\0';
 
-  if (realpath(opts->root_dir, t1) == NULL)
+  if (realpath(opts->root_dir, t1) == NULL) {
     LOG(LL_ERROR, ("realpath(%s): %d", opts->root_dir, errno));
-
-  if (!mg_is_dir(t1)) {
-    mg_http_reply(c, 400, "", "Bad web root [%s]\n", t1);
+    mg_http_reply(c, 400, "", "Bad web root [%s]\n", opts->root_dir);
+  } else if (!mg_is_dir(t1)) {
+    mg_http_reply(c, 400, "", "Invalid web root [%s]\n", t1);
   } else {
     // NOTE(lsm): Xilinx snprintf does not 0-terminate the detination for
     // the %.*s specifier, if the length is zero. Make sure hm->uri.len > 0
@@ -1106,8 +1106,11 @@ void mg_http_serve_dir(struct mg_connection *c, struct mg_http_message *hm,
     n2 = strlen(t1);
     while (n2 > 0 && t1[n2 - 1] == '/') t1[--n2] = 0;
 
-    if (realpath(t1, t2) == NULL)
+    if (realpath(t1, t2) == NULL) {
       LOG(LL_ERROR, ("realpath(%s): %d", t1, errno));
+      mg_http_reply(c, 400, "", "Error serving [%s]\n", t1);
+      return;
+    }
 
     if (mg_is_dir(t2)) {
       strncat(t2, "/index.html", sizeof(t2) - strlen(t2) - 1);
@@ -1117,7 +1120,7 @@ void mg_http_serve_dir(struct mg_connection *c, struct mg_http_message *hm,
 
     if (strlen(t2) < n1 || memcmp(t1, t2, n1) != 0) {
       // Requested file is located outside root directory, fail
-      mg_http_reply(c, 404, "", "Not found %.*s\n", (int) hm->uri.len,
+      mg_http_reply(c, 404, "", "Invalid URI [%.*s]\n", (int) hm->uri.len,
                     hm->uri.ptr);
     } else {
       FILE *fp = mg_fopen(t2, "r");
diff --git a/mongoose.h b/mongoose.h
index 20fa10e1..d07c7c01 100644
--- a/mongoose.h
+++ b/mongoose.h
@@ -270,7 +270,7 @@ typedef int socklen_t;
 #ifndef EWOULDBLOCK
 #define EWOULDBLOCK WSAEWOULDBLOCK
 #endif
-#define realpath(a, b) _fullpath((b), (a), 512)
+#define realpath(a, b) _fullpath((b), (a), MG_PATH_MAX)
 #ifndef va_copy
 #ifdef __va_copy
 #define va_copy __va_copy
diff --git a/src/arch_win32.h b/src/arch_win32.h
index c78ebd4a..45d341e3 100644
--- a/src/arch_win32.h
+++ b/src/arch_win32.h
@@ -40,7 +40,7 @@ typedef int socklen_t;
 #ifndef EWOULDBLOCK
 #define EWOULDBLOCK WSAEWOULDBLOCK
 #endif
-#define realpath(a, b) _fullpath((b), (a), 512)
+#define realpath(a, b) _fullpath((b), (a), MG_PATH_MAX)
 #ifndef va_copy
 #ifdef __va_copy
 #define va_copy __va_copy
diff --git a/src/http.c b/src/http.c
index 0eecda58..f05555f2 100644
--- a/src/http.c
+++ b/src/http.c
@@ -670,11 +670,11 @@ void mg_http_serve_dir(struct mg_connection *c, struct mg_http_message *hm,
   char t1[MG_PATH_MAX], t2[sizeof(t1)];
   t1[0] = t2[0] = '\0';
 
-  if (realpath(opts->root_dir, t1) == NULL)
+  if (realpath(opts->root_dir, t1) == NULL) {
     LOG(LL_ERROR, ("realpath(%s): %d", opts->root_dir, errno));
-
-  if (!mg_is_dir(t1)) {
-    mg_http_reply(c, 400, "", "Bad web root [%s]\n", t1);
+    mg_http_reply(c, 400, "", "Bad web root [%s]\n", opts->root_dir);
+  } else if (!mg_is_dir(t1)) {
+    mg_http_reply(c, 400, "", "Invalid web root [%s]\n", t1);
   } else {
     // NOTE(lsm): Xilinx snprintf does not 0-terminate the detination for
     // the %.*s specifier, if the length is zero. Make sure hm->uri.len > 0
@@ -686,8 +686,11 @@ void mg_http_serve_dir(struct mg_connection *c, struct mg_http_message *hm,
     n2 = strlen(t1);
     while (n2 > 0 && t1[n2 - 1] == '/') t1[--n2] = 0;
 
-    if (realpath(t1, t2) == NULL)
+    if (realpath(t1, t2) == NULL) {
       LOG(LL_ERROR, ("realpath(%s): %d", t1, errno));
+      mg_http_reply(c, 400, "", "Error serving [%s]\n", t1);
+      return;
+    }
 
     if (mg_is_dir(t2)) {
       strncat(t2, "/index.html", sizeof(t2) - strlen(t2) - 1);
@@ -697,7 +700,7 @@ void mg_http_serve_dir(struct mg_connection *c, struct mg_http_message *hm,
 
     if (strlen(t2) < n1 || memcmp(t1, t2, n1) != 0) {
       // Requested file is located outside root directory, fail
-      mg_http_reply(c, 404, "", "Not found %.*s\n", (int) hm->uri.len,
+      mg_http_reply(c, 404, "", "Invalid URI [%.*s]\n", (int) hm->uri.len,
                     hm->uri.ptr);
     } else {
       FILE *fp = mg_fopen(t2, "r");
diff --git a/test/unit_test.c b/test/unit_test.c
index acc5dce5..8d8568d1 100644
--- a/test/unit_test.c
+++ b/test/unit_test.c
@@ -496,7 +496,7 @@ static void test_http_server(void) {
 
   ASSERT(fetch(&mgr, buf, url, "GET /badroot HTTP/1.0\r\n\n") == 400);
 #if MG_ARCH == MG_ARCH_WIN32
-  ASSERT(cmpbody(buf, "Bad web root [Z:\\BAAADDD!]\n") == 0);
+  ASSERT(cmpbody(buf, "Invalid web root [Z:\\BAAADDD!]\n") == 0);
 #else
   // LOG(LL_INFO, ("--> [%s]", buf));
   ASSERT(cmpbody(buf, "Bad web root [/BAAADDD!]\n") == 0);