diff --git a/src/inc/tutil.h b/src/inc/tutil.h
index 901810c44ea7eb43e4f1ef95c8082f692e714366..a9de168fae8a300d3c03c98367b69512276a7071 100644
--- a/src/inc/tutil.h
+++ b/src/inc/tutil.h
@@ -184,7 +184,7 @@ char *strnchr(char *haystack, char needle, int32_t len, bool skipquote);
 
 char **strsplit(char *src, const char *delim, int32_t *num);
 
-void strtolower(char *dst, const char *src);
+char* strtolower(char *dst, const char *src);
 
 int64_t strnatoi(char *num, int32_t len);
 
diff --git a/src/util/src/tutil.c b/src/util/src/tutil.c
index f9bd6aace475f8ec290259c9f1b024795a49549d..d2865ec31dfe6e2b5720b6dbb7066c4b013b1ef9 100644
--- a/src/util/src/tutil.c
+++ b/src/util/src/tutil.c
@@ -140,28 +140,31 @@ char *strnchr(char *haystack, char needle, int32_t len, bool skipquote) {
   return NULL;
 }
 
-void strtolower(char *dst, const char *z) {
-  int   quote = 0;
-  char *str = z;
-  if (dst == NULL) {
-    return;
-  }
-
-  while (*str) {
-    if (*str == '\'' || *str == '"') {
-      quote = quote ^ 1;
-    }
-
-    if ((!quote) && (*str >= 'A' && *str <= 'Z')) {
-      *dst++ = *str | 0x20;
-    } else {
-      *dst++ = *str;
+char* strtolower(char *dst, const char *src) {
+  int esc = 0;
+  char quote = 0, *p = dst, c;
+
+  assert(dst != NULL);
+
+  for (c = *src++; c; c = *src++) {
+    if (esc) {
+      esc = 0;
+    } else if (quote) {
+      if (c == '\\') {
+        esc = 1;
+      } else if (c == quote) {
+        quote = 0;
+      }
+    } else if (c >= 'A' && c <= 'Z') {
+      c -= 'A' - 'a';
+    } else if (c == '\'' || c == '"') {
+      quote = c;
     }
-
-    str++;
+    *p++ = c;
   }
 
-  *dst = 0;
+  *p = 0;
+  return dst;
 }
 
 char *paGetToken(char *string, char **token, int32_t *tokenLen) {