diff --git a/backend/auspost.c b/backend/auspost.c
index d78f96e1..727b0a24 100644
--- a/backend/auspost.c
+++ b/backend/auspost.c
@@ -139,7 +139,7 @@ INTERNAL int zint_auspost(struct zint_symbol *symbol, unsigned char source[], in
                             "Invalid character at position %d in DPID (digits only for Standard Customer Barcode)",
                             not_all_digits);
             }
-            if (z_zero_fill(source, length, src_buf, 8)) {
+            if (z_zero_fill(source, length, src_buf, 8) > 0) {
                 source = src_buf;
                 length = 8;
             }
@@ -184,7 +184,7 @@ INTERNAL int zint_auspost(struct zint_symbol *symbol, unsigned char source[], in
                             "Invalid character at position %d in DPID (digits only)", i);
         }
         /* Add leading zeros as required */
-        if (z_zero_fill(source, length, src_buf, 8)) {
+        if (z_zero_fill(source, length, src_buf, 8) > 0) {
             source = src_buf;
             length = 8;
         }
diff --git a/backend/postal.c b/backend/postal.c
index b8e6a938..3a52d9ef 100644
--- a/backend/postal.c
+++ b/backend/postal.c
@@ -154,7 +154,7 @@ INTERNAL int zint_postnet(struct zint_symbol *symbol, unsigned char source[], in
     /* Stop character */
     *d++ = ascender;
 
-    h = d - dest;
+    h = (unsigned int) (d - dest);
     for (loopey = 0, writer = 0; loopey < h; loopey++, writer += 2) {
         if (dest[loopey] == ascender) {
             z_set_module(symbol, 0, writer);
@@ -390,7 +390,7 @@ static int rm4scc_enc(struct zint_symbol *symbol, const int *const posns, char *
     /* Stop character */
     *d++ = 0; /* Full */
 
-    *p_dest_len = d - dest;
+    *p_dest_len = (int) (d - dest);
 
     return KRSET[check_digit];
 }
diff --git a/backend_qt/qzint.cpp b/backend_qt/qzint.cpp
index d6f5593b..8bf376e1 100644
--- a/backend_qt/qzint.cpp
+++ b/backend_qt/qzint.cpp
@@ -98,9 +98,9 @@ namespace Zint {
         QColor color;
         int r, g, b, a;
         if (text.contains(',')) {
-            int comma1 = text.indexOf(',');
-            int comma2 = text.indexOf(',', comma1 + 1);
-            int comma3 = text.indexOf(',', comma2 + 1);
+            qsizetype comma1 = text.indexOf(',');
+            qsizetype comma2 = text.indexOf(',', comma1 + 1);
+            qsizetype comma3 = text.indexOf(',', comma2 + 1);
             int black = 100 - text.mid(comma3 + 1).toInt();
             int val = 100 - text.mid(0, comma1).toInt();
             r = (int) roundf((0xFF * val * black) / 10000.0f);
@@ -302,7 +302,7 @@ namespace Zint {
                 QByteArray bstr = m_text.toUtf8();
                 /* Note do our own rotation */
                 m_error = ZBarcode_Encode_and_Buffer_Vector(m_zintSymbol, (unsigned char *) bstr.data(),
-                            bstr.length(), 0);
+                            (int) bstr.length(), 0);
             } else {
                 struct zint_seg segs[maxSegs];
                 std::vector<QByteArray> bstrs;
@@ -960,7 +960,7 @@ namespace Zint {
             cpy_bytearray_left(m_zintSymbol->outfile, filename.toUtf8(), ARRAY_SIZE(m_zintSymbol->outfile) - 1);
             if (m_segs.empty()) {
                 QByteArray bstr = m_text.toUtf8();
-                m_error = ZBarcode_Encode_and_Print(m_zintSymbol, (unsigned char *) bstr.data(), bstr.length(),
+                m_error = ZBarcode_Encode_and_Print(m_zintSymbol, (unsigned char *) bstr.data(), (int) bstr.length(),
                                                     m_rotate_angle);
             } else {
                 struct zint_seg segs[maxSegs];
@@ -985,7 +985,7 @@ namespace Zint {
             cpy_bytearray_left(m_zintSymbol->outfile, filename.toUtf8(), ARRAY_SIZE(m_zintSymbol->outfile) - 1);
             if (m_segs.empty()) {
                 QByteArray bstr = m_text.toUtf8();
-                m_error = ZBarcode_Encode_and_Print(m_zintSymbol, (unsigned char *) bstr.data(), bstr.length(),
+                m_error = ZBarcode_Encode_and_Print(m_zintSymbol, (unsigned char *) bstr.data(), (int) bstr.length(),
                                                     m_rotate_angle);
             } else {
                 struct zint_seg segs[maxSegs];
@@ -1044,7 +1044,7 @@ namespace Zint {
             segs[i].eci = m_segs[i].m_eci;
             bstrs.push_back(m_segs[i].m_text.toUtf8());
             segs[i].source = (unsigned char *) bstrs.back().data();
-            segs[i].length = bstrs.back().length();
+            segs[i].length = (int) bstrs.back().length();
         }
         return i;
     }