diff --git a/ext/mbstring/libmbfl/filters/mbfilter_utf7imap.c b/ext/mbstring/libmbfl/filters/mbfilter_utf7imap.c
index 3ec7cbeabbe..fb2b41e6d83 100644
--- a/ext/mbstring/libmbfl/filters/mbfilter_utf7imap.c
+++ b/ext/mbstring/libmbfl/filters/mbfilter_utf7imap.c
@@ -78,6 +78,8 @@
 #include "mbfilter.h"
 #include "mbfilter_utf7imap.h"
 
+static int mbfl_filt_conv_wchar_utf7imap_flush(mbfl_convert_filter *filter);
+
 static const char *mbfl_encoding_utf7imap_aliases[] = {"mUTF-7", NULL};
 
 const mbfl_encoding mbfl_encoding_utf7imap = {
@@ -113,40 +115,34 @@ const struct mbfl_convert_vtbl vtbl_wchar_utf7imap = {
 
 #define CK(statement)	do { if ((statement) < 0) return (-1); } while (0)
 
-/*
- * UTF7-IMAP => wchar
- */
 int mbfl_filt_conv_utf7imap_wchar(int c, mbfl_convert_filter *filter)
 {
-	int s, n;
+	int s, n = -1;
 
-	n = -1;
-	if (filter->status != 0) {		/* Modified Base64 */
-		if (c >= 0x41 && c <= 0x5a) {		/* A - Z */
+	if (filter->status != 0) { /* Modified Base64 */
+		if (c >= 'A' && c <= 'Z') {
 			n = c - 65;
-		} else if (c >= 0x61 && c <= 0x7a) {	/* a - z */
+		} else if (c >= 'a' && c <= 'z') {
 			n = c - 71;
-		} else if (c >= 0x30 && c <= 0x39) {	/* 0 - 9 */
+		} else if (c >= '0' && c <= '9') {
 			n = c + 4;
-		} else if (c == 0x2b) {			/* '+' */
+		} else if (c == '+') {
 			n = 62;
-		} else if (c == 0x2c) {			/* ',' */
+		} else if (c == ',') {
 			n = 63;
 		}
+
 		if (n < 0 || n > 63) {
-			if (c == 0x2d) {
-				if (filter->status == 1) {		/* "&-" -> "&" */
-					CK((*filter->output_function)(0x26, filter->data));
+			if (c == '-') {
+				if (filter->status == 1) { /* "&-" -> "&" */
+					CK((*filter->output_function)('&', filter->data));
 				}
-			} else if (c >= 0 && c < 0x80) {	/* ASCII exclude '-' */
+			} else if (c >= 0 && c < 0x80) { /* ASCII exclude '-' */
 				CK((*filter->output_function)(c, filter->data));
-			} else {		/* illegal character */
-				s = c & MBFL_WCSGROUP_MASK;
-				s |= MBFL_WCSGROUP_THROUGH;
-				CK((*filter->output_function)(s, filter->data));
+			} else { /* illegal character */
+				CK((*filter->output_function)(c | MBFL_WCSGROUP_THROUGH, filter->data));
 			}
-			filter->cache = 0;
-			filter->status = 0;
+			filter->cache = filter->status = 0;
 			return c;
 		}
 	}
@@ -154,14 +150,12 @@ int mbfl_filt_conv_utf7imap_wchar(int c, mbfl_convert_filter *filter)
 	switch (filter->status) {
 	/* directly encoded characters */
 	case 0:
-		if (c == 0x26) {	/* '&'  shift character */
+		if (c == '&') { /* shift character */
 			filter->status++;
-		} else if (c >= 0x20 && c <= 0x7E) {	/* ASCII */
+		} else if (c >= 0x20 && c <= 0x7E) { /* ASCII */
 			CK((*filter->output_function)(c, filter->data));
-		} else {		/* illegal character */
-			s = c & MBFL_WCSGROUP_MASK;
-			s |= MBFL_WCSGROUP_THROUGH;
-			CK((*filter->output_function)(s, filter->data));
+		} else { /* illegal character */
+			CK((*filter->output_function)(c | MBFL_WCSGROUP_THROUGH, filter->data));
 		}
 		break;
 
@@ -188,10 +182,8 @@ int mbfl_filt_conv_utf7imap_wchar(int c, mbfl_convert_filter *filter)
 			filter->cache = n;
 			if (s >= MBFL_WCSPLANE_SUPMIN && s < MBFL_WCSPLANE_SUPMAX) {
 				CK((*filter->output_function)(s, filter->data));
-			} else {		/* illegal character */
-				s &= MBFL_WCSGROUP_MASK;
-				s |= MBFL_WCSGROUP_THROUGH;
-				CK((*filter->output_function)(s, filter->data));
+			} else { /* illegal character */
+				CK((*filter->output_function)(s | MBFL_WCSGROUP_THROUGH, filter->data));
 			}
 		} else {
 			filter->cache = n;
@@ -200,9 +192,7 @@ int mbfl_filt_conv_utf7imap_wchar(int c, mbfl_convert_filter *filter)
 			if (s < 0x20 || s > 0x7E || s == '&') {
 				CK((*filter->output_function)(s, filter->data));
 			} else {
-				s &= MBFL_WCSGROUP_MASK;
-				s |= MBFL_WCSGROUP_THROUGH;
-				CK((*filter->output_function)(s, filter->data));
+				CK((*filter->output_function)(s | MBFL_WCSGROUP_THROUGH, filter->data));
 			}
 		}
 		break;
@@ -228,10 +218,8 @@ int mbfl_filt_conv_utf7imap_wchar(int c, mbfl_convert_filter *filter)
 			filter->cache = n;
 			if (s >= MBFL_WCSPLANE_SUPMIN && s < MBFL_WCSPLANE_SUPMAX) {
 				CK((*filter->output_function)(s, filter->data));
-			} else {		/* illegal character */
-				s &= MBFL_WCSGROUP_MASK;
-				s |= MBFL_WCSGROUP_THROUGH;
-				CK((*filter->output_function)(s, filter->data));
+			} else { /* illegal character */
+				CK((*filter->output_function)(s | MBFL_WCSGROUP_THROUGH, filter->data));
 			}
 		} else {
 			filter->cache = n;
@@ -240,9 +228,7 @@ int mbfl_filt_conv_utf7imap_wchar(int c, mbfl_convert_filter *filter)
 			if (s < 0x20 || s > 0x7E || s == '&') {
 				CK((*filter->output_function)(s, filter->data));
 			} else {
-				s &= MBFL_WCSGROUP_MASK;
-				s |= MBFL_WCSGROUP_THROUGH;
-				CK((*filter->output_function)(s, filter->data));
+				CK((*filter->output_function)(s | MBFL_WCSGROUP_THROUGH, filter->data));
 			}
 		}
 		break;
@@ -263,10 +249,8 @@ int mbfl_filt_conv_utf7imap_wchar(int c, mbfl_convert_filter *filter)
 			filter->cache = 0;
 			if (s >= MBFL_WCSPLANE_SUPMIN && s < MBFL_WCSPLANE_SUPMAX) {
 				CK((*filter->output_function)(s, filter->data));
-			} else {		/* illegal character */
-				s &= MBFL_WCSGROUP_MASK;
-				s |= MBFL_WCSGROUP_THROUGH;
-				CK((*filter->output_function)(s, filter->data));
+			} else { /* illegal character */
+				CK((*filter->output_function)(s | MBFL_WCSGROUP_THROUGH, filter->data));
 			}
 		} else {
 			filter->cache = 0;
@@ -275,9 +259,7 @@ int mbfl_filt_conv_utf7imap_wchar(int c, mbfl_convert_filter *filter)
 			if (s < 0x20 || s > 0x7E || s == '&') {
 				CK((*filter->output_function)(s, filter->data));
 			} else {
-				s &= MBFL_WCSGROUP_MASK;
-				s |= MBFL_WCSGROUP_THROUGH;
-				CK((*filter->output_function)(s, filter->data));
+				CK((*filter->output_function)(s | MBFL_WCSGROUP_THROUGH, filter->data));
 			}
 		}
 		break;
@@ -304,15 +286,11 @@ static const unsigned char mbfl_utf7imap_base64_table[] =
    0x30,0x31,0x32,0x33,0x34,0x35,0x36,0x37,0x38,0x39,0x2b,0x2c,0x00
 };
 
-/*
- * wchar => UTF7-IMAP
- */
 int mbfl_filt_conv_wchar_utf7imap(int c, mbfl_convert_filter *filter)
 {
-	int n, s;
+	int n = 0, s;
 
-	n = 0;
-	if (c == 0x26) {
+	if (c == '&') {
 		n = 1;
 	} else if ((c >= 0x20 && c <= 0x7e) || c == 0) {
 		n = 2;
@@ -350,10 +328,10 @@ int mbfl_filt_conv_wchar_utf7imap(int c, mbfl_convert_filter *filter)
 		CK((*filter->output_function)(mbfl_utf7imap_base64_table[(s >> 4) & 0x3f], filter->data));
 		if (n != 0) {
 			CK((*filter->output_function)(mbfl_utf7imap_base64_table[(s << 2) & 0x3c], filter->data));
-			CK((*filter->output_function)(0x2d, filter->data));		/* '-' */
+			CK((*filter->output_function)('-', filter->data));
 			CK((*filter->output_function)(c, filter->data));
 			if (n == 1) {
-				CK((*filter->output_function)(0x2d, filter->data));		/* '-' */
+				CK((*filter->output_function)('-', filter->data));
 			}
 			filter->status = 0;
 		} else {
@@ -369,10 +347,10 @@ int mbfl_filt_conv_wchar_utf7imap(int c, mbfl_convert_filter *filter)
 		CK((*filter->output_function)(mbfl_utf7imap_base64_table[(s >> 2) & 0x3f], filter->data));
 		if (n != 0) {
 			CK((*filter->output_function)(mbfl_utf7imap_base64_table[(s << 4) & 0x30], filter->data));
-			CK((*filter->output_function)(0x2d, filter->data));		/* '-' */
+			CK((*filter->output_function)('-', filter->data));
 			CK((*filter->output_function)(c, filter->data));
 			if (n == 1) {
-				CK((*filter->output_function)(0x2d, filter->data));		/* '-' */
+				CK((*filter->output_function)('-', filter->data));
 			}
 			filter->status = 0;
 		} else {
@@ -387,10 +365,10 @@ int mbfl_filt_conv_wchar_utf7imap(int c, mbfl_convert_filter *filter)
 		CK((*filter->output_function)(mbfl_utf7imap_base64_table[(s >> 6) & 0x3f], filter->data));
 		CK((*filter->output_function)(mbfl_utf7imap_base64_table[s & 0x3f], filter->data));
 		if (n != 0) {
-			CK((*filter->output_function)(0x2d, filter->data));		/* '-' */
+			CK((*filter->output_function)('-', filter->data));
 			CK((*filter->output_function)(c, filter->data));
 			if (n == 1) {
-				CK((*filter->output_function)(0x2d, filter->data));		/* '-' */
+				CK((*filter->output_function)('-', filter->data));
 			}
 			filter->status = 0;
 		} else {
@@ -408,21 +386,18 @@ int mbfl_filt_conv_wchar_utf7imap(int c, mbfl_convert_filter *filter)
 
 }
 
-int mbfl_filt_conv_wchar_utf7imap_flush(mbfl_convert_filter *filter)
+static int mbfl_filt_conv_wchar_utf7imap_flush(mbfl_convert_filter *filter)
 {
-	int status, cache;
+	int status = filter->status, cache = filter->cache;
+	filter->status = filter->cache = 0;
 
-	status = filter->status;
-	cache = filter->cache;
-	filter->status = 0;
-	filter->cache = 0;
 	/* flush fragments */
 	switch (status) {
 	case 1:
 		CK((*filter->output_function)(mbfl_utf7imap_base64_table[(cache >> 10) & 0x3f], filter->data));
 		CK((*filter->output_function)(mbfl_utf7imap_base64_table[(cache >> 4) & 0x3f], filter->data));
 		CK((*filter->output_function)(mbfl_utf7imap_base64_table[(cache << 2) & 0x3c], filter->data));
-		CK((*filter->output_function)(0x2d, filter->data));		/* '-' */
+		CK((*filter->output_function)('-', filter->data));
 		break;
 
 	case 2:
@@ -430,14 +405,14 @@ int mbfl_filt_conv_wchar_utf7imap_flush(mbfl_convert_filter *filter)
 		CK((*filter->output_function)(mbfl_utf7imap_base64_table[(cache >> 8) & 0x3f], filter->data));
 		CK((*filter->output_function)(mbfl_utf7imap_base64_table[(cache >> 2) & 0x3f], filter->data));
 		CK((*filter->output_function)(mbfl_utf7imap_base64_table[(cache << 4) & 0x30], filter->data));
-		CK((*filter->output_function)(0x2d, filter->data));		/* '-' */
+		CK((*filter->output_function)('-', filter->data));
 		break;
 
 	case 3:
 		CK((*filter->output_function)(mbfl_utf7imap_base64_table[(cache >> 12) & 0x3f], filter->data));
 		CK((*filter->output_function)(mbfl_utf7imap_base64_table[(cache >> 6) & 0x3f], filter->data));
 		CK((*filter->output_function)(mbfl_utf7imap_base64_table[cache & 0x3f], filter->data));
-		CK((*filter->output_function)(0x2d, filter->data));		/* '-' */
+		CK((*filter->output_function)('-', filter->data));
 		break;
 	}
 	return 0;
diff --git a/ext/mbstring/libmbfl/filters/mbfilter_utf7imap.h b/ext/mbstring/libmbfl/filters/mbfilter_utf7imap.h
index 19ab934da07..7c096ce5b41 100644
--- a/ext/mbstring/libmbfl/filters/mbfilter_utf7imap.h
+++ b/ext/mbstring/libmbfl/filters/mbfilter_utf7imap.h
@@ -38,6 +38,5 @@ extern const struct mbfl_convert_vtbl vtbl_wchar_utf7imap;
 
 int mbfl_filt_conv_utf7imap_wchar(int c, mbfl_convert_filter *filter);
 int mbfl_filt_conv_wchar_utf7imap(int c, mbfl_convert_filter *filter);
-int mbfl_filt_conv_wchar_utf7imap_flush(mbfl_convert_filter *filter);
 
 #endif /* MBFL_MBFILTER_UTF7IMAP_H */