diff --git a/htp/bstr.c b/htp/bstr.c
index b34d3c0b..928e3a10 100644
--- a/htp/bstr.c
+++ b/htp/bstr.c
@@ -339,7 +339,7 @@ bstr *bstr_to_lowercase(bstr *b) {
 
     size_t i = 0;
     while (i < len) {
-        data[i] = tolower(data[i]);
+        data[i] = (uint8_t)tolower(data[i]);
         i++;
     }
 
diff --git a/htp/htp_base64.c b/htp/htp_base64.c
index 0b03a6f3..db8fef9a 100644
--- a/htp/htp_base64.c
+++ b/htp/htp_base64.c
@@ -103,7 +103,7 @@ int htp_base64_decode(htp_base64_decoder *decoder, const void *_code_in, int len
                     }
                     fragment = (char) htp_base64_decode_single(*codechar++);
                 } while (fragment < 0);
-                *plainchar = (fragment & 0x03f) << 2;
+                *plainchar = (unsigned char) ((fragment & 0x03f) << 2);
                 /* fall through */
 
                 case step_b:
@@ -116,7 +116,7 @@ int htp_base64_decode(htp_base64_decoder *decoder, const void *_code_in, int len
                     fragment = (char) htp_base64_decode_single(*codechar++);
                 } while (fragment < 0);
                 *plainchar++ |= (fragment & 0x030) >> 4;
-                *plainchar = (fragment & 0x00f) << 4;                
+                *plainchar = (unsigned char) ((fragment & 0x00f) << 4);
                 if (--length_out == 0) {
                     return plainchar - plaintext_out;
                 }
@@ -132,7 +132,7 @@ int htp_base64_decode(htp_base64_decoder *decoder, const void *_code_in, int len
                     fragment = (char) htp_base64_decode_single(*codechar++);
                 } while (fragment < 0);
                 *plainchar++ |= (fragment & 0x03c) >> 2;
-                *plainchar = (fragment & 0x003) << 6;
+                *plainchar = (unsigned char) ((fragment & 0x003) << 6);
                 if (--length_out == 0) {
                     return plainchar - plaintext_out;
                 }
diff --git a/htp/htp_config.c b/htp/htp_config.c
index 41b5cb4c..767458f0 100644
--- a/htp/htp_config.c
+++ b/htp/htp_config.c
@@ -724,11 +724,11 @@ void htp_config_set_bestfit_map(htp_cfg_t *cfg, enum htp_decoder_ctx_t ctx, void
 void htp_config_set_bestfit_replacement_byte(htp_cfg_t *cfg, enum htp_decoder_ctx_t ctx, int b) {
     if (ctx >= HTP_DECODER_CONTEXTS_MAX) return;
 
-    cfg->decoder_cfgs[ctx].bestfit_replacement_byte = b;
+    cfg->decoder_cfgs[ctx].bestfit_replacement_byte = (unsigned char) b;
 
     if (ctx == HTP_DECODER_DEFAULTS) {
         for (size_t i = 0; i < HTP_DECODER_CONTEXTS_MAX; i++) {
-            cfg->decoder_cfgs[i].bestfit_replacement_byte = b;
+            cfg->decoder_cfgs[i].bestfit_replacement_byte = (unsigned char) b;
         }
     }
 }
diff --git a/htp/htp_response.c b/htp/htp_response.c
index a637c834..dec1222b 100644
--- a/htp/htp_response.c
+++ b/htp/htp_response.c
@@ -401,7 +401,7 @@ htp_status_t htp_connp_RES_BODY_CHUNKED_LENGTH(htp_connp_t *connp) {
 
         // Have we reached the end of the line? Or is this not chunked after all?
         if (connp->out_next_byte == LF ||
-                (!is_chunked_ctl_char(connp->out_next_byte) && !data_probe_chunk_length(connp))) {
+                (!is_chunked_ctl_char((unsigned char) connp->out_next_byte) && !data_probe_chunk_length(connp))) {
             unsigned char *data;
             size_t len;