diff --git a/include/strutils.h b/include/strutils.h
index 7969a84d0..a62f72493 100644
--- a/include/strutils.h
+++ b/include/strutils.h
@@ -315,16 +315,20 @@ static inline size_t ltrim_whitespace(unsigned char *str)
 
 /* Removes left-hand, right-hand and repeating whitespaces.
  */
-static inline size_t normalize_whitespace(unsigned char *str)
+static inline size_t __normalize_whitespace(
+				const unsigned char *src,
+				size_t sz,
+				unsigned char *dst,
+				size_t len)
 {
-	size_t i, x, sz = strlen((char *) str);
+	size_t i, x = 0;
 	int nsp = 0, intext = 0;
 
 	if (!sz)
-		return 0;
+		goto done;
 
-	for (i = 0, x = 0; i < sz; ) {
-		if (isspace(str[i]))
+	for (i = 0, x = 0; i < sz && x < len - 1;  ) {
+		if (isspace(src[i]))
 			nsp++;
 		else
 			nsp = 0, intext = 1;
@@ -332,14 +336,21 @@ static inline size_t normalize_whitespace(unsigned char *str)
 		if (nsp > 1 || (nsp && !intext))
 			i++;
 		else
-			str[x++] = str[i++];
+			dst[x++] = src[i++];
 	}
-	if (nsp)		/* tailing space */
+	if (nsp && x > 0)		/* tailing space */
 		x--;
-	str[x] = '\0';
+done:
+	dst[x] = '\0';
 	return x;
 }
 
+static inline size_t normalize_whitespace(unsigned char *str)
+{
+	size_t sz = strlen((char *) str);
+	return __normalize_whitespace(str, sz, str, sz + 1);
+}
+
 static inline void strrep(char *s, int find, int replace)
 {
 	while (s && *s && (s = strchr(s, find)) != NULL)
diff --git a/lib/strutils.c b/lib/strutils.c
index 5b5e686aa..68b664748 100644
--- a/lib/strutils.c
+++ b/lib/strutils.c
@@ -1175,17 +1175,26 @@ static int test_strutils_cmp_paths(int argc, char *argv[])
 
 static int test_strutils_normalize(int argc, char *argv[])
 {
-	unsigned char *str;
-	size_t sz;
+	unsigned char *src, *dst;
+	size_t sz, len;
 
 	if (argc < 2)
 		return EXIT_FAILURE;
 
-	str = (unsigned char *) strdup(argv[1]);
-	sz = normalize_whitespace(str);
+	src =  (unsigned char *) strdup(argv[1]);
+	len = strlen((char *) src);
+	dst = malloc(len + 1);
 
-	printf("'%s' --> '%s' [sz=%zu]\n", argv[1], str, sz);
-	free(str);
+	/* two buffers */
+	sz = __normalize_whitespace(src, len, dst, len + 1);
+	printf("1: '%s' --> '%s' [sz=%zu]\n", src, dst, sz);
+
+	/* one buffer */
+	sz = normalize_whitespace(src);
+	printf("2: '%s' --> '%s' [sz=%zu]\n", argv[1], src, sz);
+
+	free(src);
+	free(dst);
 
 	return EXIT_SUCCESS;
 }